📝 [#4771] Document 3.0 breaking changes w/r to price logic

... and other things that should've had their documentation
added already but I neglected to do so.

docs/installation/index.rst

@@ -29,5 +29,6 @@ and expertise.
    form_hosting
    redis
    issues/index
-   upgrade-240
+   upgrade-300
    upgrade-250
+   upgrade-240

docs/installation/upgrade-300.rst

@@ -0,0 +1,49 @@
+.. _installation_upgrade_300:
+
+===================================
+Upgrade details to Open Forms 3.0.0
+===================================
+
+Open Forms 3.0 is a major version release that contains some breaking changes. As always
+we try to limit the impact of breaking changes through automatic migrations, and this
+release is no different, but there are some subtle changes in behaviour that you should
+be aware of, as they may require additional manual actions.
+
+.. contents:: Jump to
+   :depth: 1
+   :local:
+
+Removal of price logic
+======================
+
+Price logic rules are removed in favour of setting the submission price via a form
+variable and normal logic rules. The conversion is automatic.
+
+There is a slight change in behaviour. When no price logic rules matched the trigger
+condition, the price set on the related product was used. This can lead to surprises
+and wrong amounts being paid due to logical errors in the form itself.
+
+The new behaviour will (deliberately) cause a crash that will show to the end-user
+as "something unexpectedly went wrong", since we refuse to make any (likely wrong)
+assumptions about the amount that needs to be paid. Crash information is visible
+in the error monitoring if that's set up correctly.
+
+.. note:: Existing, automatically converted forms are crash-free because we create an
+   explicit fallback logic rule that mimicks the old behaviour.
+
+Form components/fields changes
+==============================
+
+Removal of legacy translations conversion
+-----------------------------------------
+
+Old (from before Open Forms 2.4) form export files containing form field translations
+in the legacy format are now ignored instead of converted to the new format. We
+recommend re-creating the exports on a newer version of Open Forms.
+
+Password component removed
+--------------------------
+
+The password component was deprecated a long time ago, and has now been removed. If you
+need to replace it anywhere, use a regular textfield component instead, but you really
+shouldn't be asking users for passwords.

docs/manual/forms/basics.rst

@@ -199,7 +199,7 @@ product bevat een prijs die gebruikt kan worden als betaald moet worden voor
 het product. Betaling kan ingesteld worden door de juiste **Betaalprovider** te
 selecteren.
 
-Er zijn drie manieren om de prijs van een inzending te bepalen:
+Er zijn twee manieren om de prijs van een inzending te bepalen:
 
 **Gebruik de prijs van het gekoppeld product**
 
@@ -226,10 +226,9 @@ te activeren.
 
 **Gebruik prijslogica**
 
-Voor eenvoudige condities kan je prijslogic instellen. Onder een bepaalde conditie geldt
-een bepaalde, vaste, prijs. Indien aan geen enkele conditie voldaan is, dan wordt de
-prijs van het gekoppeld product gebruikt. De **Prijslogica** volgt verder dezelfde
-regels als reguliere **Logica**.
+.. versionremoved:: 3.0
+
+   De prijslogica is vervangen door gewone logica + gebruik van een variabele.
 
 Zie ook: :ref:`configuration_payment_index`