Fix mysql_user on_new_username IndexError (#642)

* fix tuple indexerror when no accounts are found

* Fix tests for update_password not executed

* Add test for case where existing user have different password

* lint to prevent warning about jinja templating in when clause

* Refactor get_existing_authentication to return a list of all row found

Previously we were returning only the first row found. We need to be
able to see if there is a difference in the existing passwords.

* Refactor host option to be optional

This make it possible to use the same method from mysql_user to help
update_password retrieve existing password for all account with the same
username independently of their hostname. And from mysql_info to get
the password of a specif user using WHERE user = '' AND host = ''

* Add change log fragment

* Add link to the PR in the change log

* lint for ansible devel

* Fix templating type error could not cconvert to bool with ansible devel

* Revert changes made for ansible-devel that broke tests for Ansible 2.15

* Revert changes made for ansible-devel that broke tests

* Cut unnecessary set, uniqueness is ensured by the group_by in the query

* Cut auth plugin from returned values when multiple existing auths exists

Discussed here:
https://github.com/ansible-collections/community.mysql/pull/642/files#r1649720519

* fix convertion of list(dict) to list(tuple)

* Fix test for empty password on MySQL 8+

tests/integration/targets/test_mysql_user/tasks/utils/assert_user_password.yml

@@ -1,6 +1,6 @@
 ---
 - name: Utils | Assert user password | Apply update_password to {{ username }}
-  mysql_user:
+  community.mysql.mysql_user:
     login_user: '{{ mysql_parameters.login_user }}'
     login_password: '{{ mysql_parameters.login_password }}'
     login_host: '{{ mysql_parameters.login_host }}'
@@ -13,16 +13,17 @@
   register: result
 
 - name: Utils | Assert user password | Assert a change occurred
-  assert:
+  ansible.builtin.assert:
     that:
-      - "result.changed | bool == {{ expect_change }} | bool"
-      - "result.password_changed == {{ expect_password_change }}"
+      - result.changed | bool == expect_change | bool
+      - result.password_changed == expect_password_change
 
-- name: Utils | Assert user password | Query user {{ username }}
-  command: "{{ mysql_command }} -BNe \"SELECT plugin, authentication_string FROM mysql.user where user='{{ username }}' and host='{{ host }}'\""
+- name: Utils | Assert user password | Assert expect_hash is in user stdout for {{ username }}
+  ansible.builtin.command: >-
+    {{ mysql_command }} -BNe "SELECT plugin, authentication_string
+    FROM mysql.user where user='{{ username }}' and host='{{ host }}'"
   register: existing_user
-
-- name: Utils | Assert user password | Assert expect_hash is in user stdout
-  assert:
-    that:
-      - "'mysql_native_password\t{{ expect_password_hash }}' in existing_user.stdout_lines"
+  changed_when: false
+  failed_when: pattern not in existing_user.stdout_lines
+  vars:
+    pattern: "mysql_native_password\t{{ expect_password_hash }}"