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+
+# Session handling
+
+```mermaid
+erDiagram
+  UniloginAccessToken {
+      string accessToken
+      int expires
+      string refreshToken
+      int values__refresh_expires_in
+      int values__id_token
+  }
+```
+
+# DingUniloginUser
+
+```mermaid
+erDiagram
+    DingUniloginUser {
+        string name
+        string authname
+        string wsuser
+        string wspass
+        string_array institutionsIds
+        int_array municipalityIds
+        object_array institutions
+    }
+```
+
+`name` is the same as the Unilogin username
+
+# Publizon Libraries (local db table)
+
+```mermaid
+erDiagram
+    publizon_libraries {
+      string retailer_id
+      string library_name
+      string unilogin_id
+      string retailer_key_code
+      string subscribed_users
+      string municipality_id
+    }
+```
+
+# Institutions og municipalities
+
+```mermaid
+erDiagram
+    institution {
+      string instnr
+      string instnavn
+      string type
+      string typenavn
+      string adresse
+      string bynavn
+      string postnr
+      string telefonnr
+      string mailadresse
+      string www
+      int kommunenr
+    }
+```
+
+## institutionIds
+
+Institution ids are collected via the `DingUniloginWSIbruger` client via `hentBrugersInstitutionsTilknytninger` SOAP service
+
+## municipalitiesIds
+
+Municipalities is only represented as id's.
+
+Municipalities are fetched via the `DingUniloginUser::getInstitutionMunicipalities(institutionIds)` method:
+
+* Fake municipalities are established via `_ding_unilogin_get_nonstitution_municipalities` that gets its data from: `_ding_unilogin_get_nonstitutions` that gets the institutions from a setting (variable) called: `ding_unilogin_nonstitutions`
+* InstitutionIds are iterated and every institution is fetched by the `DingUniloginWSIinst` client via the  `hentInstitution` service
+* If a fake institution exists with current institutionId then use the `kommunenr` from that
+* (side effect) `DingUniloginUser.institutions` are being populated in the iteration with the institution
+* `insititution.kommunenr` is added to the `municipalityIds` array
+* The  `municipalityIds` array is set on `DingUniloginUser.municipalityIds`
+* The `municipalityIds` array is being returned
+
+# Library/libraries
+
+```mermaid
+erDiagram
+    PublizonConfiguredLibrary {
+      int retailer_id
+      string library_name
+      string unilogin_id
+      string municipality_id
+      string retailer_key_code
+      string subscribed_users
+    }
+```
+
+Libraries (`PublizonConfiguredLibrary`) are stored in the db in the table: `publizon_libraries` they are fetched by the function: `publizon_get_libraries()` which keys them by `retailer_id`.
+
+Afterwards the libraries are being filtered by the municipalities connected to the user.
+
+## The usage/meaning of a library
+
+If there is multiple libraries connected to the user, only the first one is being used.
+
+The unilogin_id from the library is being tied to the Drupal user and is being used in future contexts.
+
+# Services
+
+## Unilogin services
+
+### Base class: DingUniloginServiceBase
+
+Uses two methods: `call` and `callWithAuth` depending on if the request needs authentication
+
+`callWithAuth` uses wsuser and wspasswd tied to the `DingUniloginUser` object
+
+### DingUniloginWSIbruger (Unilogin API)
+
+#### WSDL Url
+
+```
+https://wsibruger.unilogin.dk/wsibruger-v6/ws?WSDL
+```
+
+#### Actions
+
+**hentBrugersInstitutionsTilknytninger**: Finds institutions connected to a user.
+
+ ---
+
+### DingUniloginWSIinst (Unilogin API)
+
+#### WSDL Url
+
+```
+https://wsiinst.unilogin.dk/wsiinst-v5/ws?WSDL
+```
+
+#### Actions
+
+**hentInstitution**: Loads a institution given its id.
+
+## Publizon services
+
+### Base class: PublizonClient
+
+Makes sure that following params are used as well:
+
+* ':languagecode': empty string
+* ':clientid': publizon client id
+* ':retailerid': retailer id tied to user (from library)
+* ':retailerkeycode': retailer id tied to user (from library)
+
+### PublizonUserClient (Publizon API)
+
+#### Methods
+
+##### getSupportId
+
+**Endpoint**: get_friendly_cardnumber
+
+**Action**: GetFriendlyCardnumber
+
+**Params**: `pub:cardnumber` (uniid), `retailer_id` (from library)
+
+### PublizonLoanClient  (Publizon API)
+
+#### Methods
+
+##### createLoan
+
+**Endpoint**: createloan.asmx
+
+**Action**: CreateLoan
+
+**Params**: `pub:ebookid` (isbn), `retailer_id` (from library), `pub:cardnumber` (uniid (username)), `pub:pincode` (empty), `pub:institutionid`, `pub:format` (empty string), `pub:mobipocketid` (empty string), `pub:institutionTags` (array of `pub:string` => $institution_tags (often empty))
+
+---
+
+##### getLibraryUserOrderList
+
+**Endpoint**: getlibraryuserorderlist.asmx
+
+**Action**: GetLibraryUserOrderList
+
+**Params**: `retailer_id` (from library), `pub:cardnumber` (uniid (username))
+
+# Login flows
+
+## Unilogin
+
+Login flow at Unilogin
+
+```mermaid
+sequenceDiagram
+    participant US as Unilogin Services
+    participant EG as Ereolen GO
+
+    EG->>US: User clicks login at Ereolen GO
+    US->>EG: User authenticated
+    EG-->>US: Get access token *1
+    EG-->>US: Get user info
+    Note over EG: Access token sent as argument
+    Note over US: Most important data her is: uniid
+    EG->>EG: DingUniloginUser instantiated
+    Note over EG: Username = Unilogin uniid
+    EG-->>US: Get institution ids tied to the user
+    EG-->>EG: Get Nonstitution Municipalities
+    Note over EG: Municipalites are stored in a variable called:<br/> ding_unilogin_nonstitutions *2
+    EG-->>EG: An array of municpalities is tied to the user *3
+    EG-->>US: Get Institution
+    Note over EG: For each institution ids tied to the user
+    EG-->>EG: Get library
+    Note over EG: Lookup in local DB table ("publizon_libraries") *4
+    EG-->>EG: Ding User Authenticate
+    Note over EG: library.unilogin_id is connected to the<br/> Ding user object in the extra.attributes.unilogin property
+    EG->>EG: publizon_auth_single_sign_on
+    Note over EG: Retailer id and support id is added to Drupal user.data
+
+
+```
+
+1) It seems like the access token is primarily used to fetch userinfo about user in not in subsequent calls like: getUserLoans performLoan etc.
+
+2) Only one nonstitution municipality is stored:
+
+```bash
+ding_unilogin_nonstitutions:
+  A04441:
+    institution_id: A04441
+    municipality_kommunenr: '101'
+    municipality_kommune: '101'
+```
+
+The municipality is represented in the `publizon_libraries` table:
+
+```mysql
++-------------+--------------+-------------+-------------------+------------------+-----------------+
+| retailer_id | library_name | unilogin_id | retailer_key_code | subscribed_users | municipality_id |
++-------------+--------------+-------------+-------------------+------------------+-----------------+
+| 810         | København    | 101         | xxxxxxxx          | 26915            | 101             |
++-------------+--------------+-------------+-------------------+------------------+-----------------+
+```
+
+3) For every institution stored on user there is a `kommunenr` and is collected into a municipality array:
+
+```php
+ $municipalityIds[] = $institution->kommunenr;
+ ```
+
+ However if an user institution is represented in `ding_unilogin_nonstitutions` the `kommunenr` is used from that.
+
+4) Get library by looking at the kommunenr of the first institution of the user