ansible_module_utils: Make list generation function data type aware

The list generation functions for adding and deleting members from IPA
objects create sets but are not aware of the underlying attribute data
type. Some data types need to perform special comparison, like case
insensitive string comparison, or ensure the existence of a FQDN.

This patch adds a new optional attribute to the list generation
functions, 'attr_datatype', that takes a function able to convert the
expected data (usually a string) to an object that will correctly handle
hashing and data comparison.

The functions were also modified to perform the list generation, but
still return the same data provided to the caller, withot conversion,
minimizing the required amount of code changes.

plugins/module_utils/ansible_freeipa_module.py

@@ -636,7 +636,24 @@ def api_get_basedn():
     return api.env.basedn
 
 
-def gen_add_del_lists(user_list, res_list):
+def _identity_datatype(value):
+    """Return value, providing an identity function."""
+    return value
+
+
+def gen_user_res_sets(user_list, res_list, attr_datatype=None):
+    """Generate user and result lists based on attribute datatype."""
+    if attr_datatype:
+        user_set = {attr_datatype(item) for item in (user_list or [])}
+        res_set = {attr_datatype(item) for item in (res_list or [])}
+    else:
+        user_set = set(user_list or [])
+        res_set = set(res_list or [])
+
+    return user_set, res_set
+
+
+def gen_add_del_lists(user_list, res_list, attr_datatype=None):
     """
     Generate the lists for the addition and removal of members.
 
@@ -646,18 +663,32 @@ def gen_add_del_lists(user_list, res_list):
     For the addition of new and the removal of existing members with
     action: members gen_add_list and gen_intersection_list should
     be used.
+
+    If attr_datatype is provided, all values in user_list and res_list
+    will we converted to it before the list is created.
     """
     # The user list is None, no need to do anything, return empty lists
     if user_list is None:
         return [], []
 
-    add_list = list(set(user_list or []) - set(res_list or []))
-    del_list = list(set(res_list or []) - set(user_list or []))
+    if not attr_datatype:
+        attr_datatype = _identity_datatype
+
+    user_set, res_set = gen_user_res_sets(user_list, res_list, attr_datatype)
+    add_list = list(
+        set(item for item in user_list if attr_datatype(item) not in res_set)
+    )
+    del_list = list(
+        set(
+            item for item in (res_list or [])
+            if attr_datatype(item) not in user_set
+        )
+    )
 
     return add_list, del_list
 
 
-def gen_add_list(user_list, res_list):
+def gen_add_list(user_list, res_list, attr_datatype=None):
     """
     Generate add list for addition of new members.
 
@@ -666,15 +697,26 @@ def gen_add_list(user_list, res_list):
 
     It is returning the difference of the user and res list if the user
     list is not None.
+
+    If attr_datatype is provided, all values in user_list and res_list
+    will we converted to it before the list is created.
     """
     # The user list is None, no need to do anything, return empty list
     if user_list is None:
         return []
 
-    return list(set(user_list or []) - set(res_list or []))
+    if not attr_datatype:
+        attr_datatype = _identity_datatype
+
+    _user_set, res_set = gen_user_res_sets(user_list, res_list, attr_datatype)
+    add_list = list(
+        set(item for item in user_list if attr_datatype(item) not in res_set)
+    )
+
+    return add_list
 
 
-def gen_intersection_list(user_list, res_list):
+def gen_intersection_list(user_list, res_list, attr_datatype=None):
     """
     Generate the intersection list for removal of existing members.
 
@@ -683,12 +725,26 @@ def gen_intersection_list(user_list, res_list):
 
     It is returning the intersection of the user and res list if the
     user list is not None.
+
+    If attr_datatype is provided, all values in user_list and res_list
+    will we converted to it before the list is created.
     """
     # The user list is None, no need to do anything, return empty list
     if user_list is None:
         return []
+    if not res_list:
+        return []
+
+    if not attr_datatype:
+        attr_datatype = _identity_datatype
+
+    user_set, _res_set = gen_user_res_sets(user_list, res_list, attr_datatype)
+
+    intersection_list = list(
+        set(item for item in res_list if attr_datatype(item) in user_set)
+    )
 
-    return list(set(res_list or []).intersection(set(user_list or [])))
+    return intersection_list
 
 
 def encode_certificate(cert):