mysql_role: add argument "members_must_exist" (#369)

* mysql_role: add argument "members_must_exist" (boolean, default true)

The assertion that the users supplied in the "members" argument exist is only executed when the new argument "members_must_exist" is true, to allow opt-out.

* mysql_role: add integration tests for argument members_must_exist

* add changelog fragment

* mysql_role: fix behavior of members_must_exist argument

* Update plugins/modules/mysql_role.py

Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

* Update changelogs/fragments/369_mysql_role-add-members_must_exist.yml

Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

Co-authored-by: Felix Hamme <felix.hamme@ionos.com>
Co-authored-by: Andrew Klychkov <aaklychkov@mail.ru>

tests/integration/targets/test_mysql_role/tasks/mysql_role_initial.yml

@@ -1274,6 +1274,71 @@
       that:
         - "'{{ role3 }}' not in result.query_result.0.0['Grants for {{ user1 }}@localhost']"
 
+  # test members_must_exist
+  - name: try failing on not-existing user in check-mode
+    <<: *task_params
+    mysql_role:
+      <<: *mysql_params
+      name: '{{ role0 }}'
+      state: present
+      members_must_exist: yes
+      append_members: yes
+      members:
+        - 'not_existent@localhost'
+    ignore_errors: yes
+    check_mode: yes
+  - name: assert failure
+    assert:
+      that:
+        - result is failed
+
+  - name: try failing on not-existing user in check-mode
+    <<: *task_params
+    mysql_role:
+      <<: *mysql_params
+      name: '{{ role0 }}'
+      state: present
+      members_must_exist: no
+      append_members: yes
+      members:
+        - 'not_existent@localhost'
+    check_mode: yes
+  - name: Check for lack of change
+    assert:
+      that:
+        - result is not changed
+
+  - name: try failing on not-existing user
+    <<: *task_params
+    mysql_role:
+      <<: *mysql_params
+      name: '{{ role0 }}'
+      state: present
+      members_must_exist: yes
+      append_members: yes
+      members:
+        - 'not_existent@localhost'
+    ignore_errors: yes
+  - name: assert failure
+    assert:
+      that:
+        - result is failed
+
+  - name: try failing on not-existing user
+    <<: *task_params
+    mysql_role:
+      <<: *mysql_params
+      name: '{{ role0 }}'
+      state: present
+      members_must_exist: no
+      append_members: yes
+      members:
+        - 'not_existent@localhost'
+  - name: Check for lack of change
+    assert:
+      that:
+        - result is not changed
+
   # ##########
   # Test privs
   # ##########