Deprecate support for the v2 galaxy API (#82543)

Co-authored-by: Matt Davis <6775756+nitzmahone@users.noreply.github.com>

changelogs/fragments/deprecate-v2-galaxy-api.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- ansible-galaxy - Deprecate use of the Galaxy v2 API (https://github.com/ansible/ansible/issues/81781)

lib/ansible/galaxy/api.py

@@ -133,6 +133,15 @@ def g_connect(versions):
                                    % (method.__name__, ", ".join(versions), ", ".join(available_versions),
                                       self.name, self.api_server))
 
+            # Warn only when we know we are talking to a collections API
+            if common_versions == {'v2'}:
+                display.deprecated(
+                    'The v2 Ansible Galaxy API is deprecated and no longer supported. '
+                    'Ensure that you have configured the ansible-galaxy CLI to utilize an '
+                    'updated and supported version of Ansible Galaxy.',
+                    version='2.20'
+                )
+
             return method(self, *args, **kwargs)
         return wrapped
     return decorator