Add changelog fragment with PostgreSQL migration announcement (#1384)

changelogs/fragments/postgresql-migration.yml

@@ -0,0 +1,10 @@
+major_changes:
+- |
+  For community.general 2.0.0, the ``postgresql`` modules and plugins will be moved to the `community.postgresql <https://galaxy.ansible.com/community/postgresql>`_ collection.
+  A redirection will be inserted so that users using ansible-base 2.10 or newer do not have to change anything.
+
+  If you use Ansible 2.9 and explicitly use ``postgresql`` content from this collection, you will need to adjust your playbooks and roles to use FQCNs starting with ``community.postgresql.`` instead of ``community.general.``,
+  for example replace ``community.general.postgresql_info`` in a task by ``community.postgresql.postgresql_info``.
+
+  If you use ansible-base and installed ``community.general`` manually and rely on the ``postgresql`` content, you have to make sure to install the ``community.postgresql`` collection as well.
+  If you are using FQCNs, i.e. ``community.general.postgresql_info`` instead of ``postgresql_info``, it will continue working, but we still recommend to adjust the FQCNs as well.