Allow user to specify namespace for standalone roles (#1451)

This change allows user to specify the desired namespace under which
the role is expected to be published. This allows us to better test
the role as it was installed, including performing syntax check on
test playbooks.

Previous implementation was forcing user to convert its author field
to a namespace compatible string. We no longer need this as
galaxy-importer does not have any problem when it encounters unknown
fields. Namespace is also used in collections, so it would be easier
for to remember for users.

Author: ssbarnea

src/ansiblelint/_prerun.py

@@ -154,11 +154,13 @@ def _install_galaxy_role() -> None:
     if 'galaxy_info' not in yaml:
         return
     role_name = yaml['galaxy_info'].get('role_name', None)
-    role_author = yaml['galaxy_info'].get('author', None)
+    role_namespace = yaml['galaxy_info'].get('namespace', None)
+    if not role_namespace:
+        role_namespace = yaml['galaxy_info'].get('author', None)
     if not role_name:
         role_name = pathlib.Path(".").absolute().name
         role_name = re.sub(r'^{0}'.format(re.escape('ansible-role-')), '', role_name)
-    fqrn = f"{role_author}.{role_name}"
+    fqrn = f"{role_namespace}.{role_name}"
     if not re.match(r"[a-z0-9][a-z0-9_]+\.[a-z][a-z0-9_]+$", fqrn):
         print(
             f"""\
@@ -167,7 +169,7 @@ def _install_galaxy_role() -> None:
 
 galaxy_info:
   role_name: my_name  # if absent directory name hosting role is used instead
-  author: my_galaxy_namespace
+  namespace: my_galaxy_namespace  # if absent, author is used instead
 
 Namespace: https://galaxy.ansible.com/docs/contributing/namespaces.html#galaxy-namespace-limitations
 Role: https://galaxy.ansible.com/docs/contributing/creating_role.html#role-names
@@ -177,7 +179,7 @@ def _install_galaxy_role() -> None:
         sys.exit(INVALID_PREREQUISITES_RC)
     p = pathlib.Path(f"{options.project_dir}/.cache/roles")
     p.mkdir(parents=True, exist_ok=True)
-    link_path = p / f"{role_author}.{role_name}"
+    link_path = p / f"{role_namespace}.{role_name}"
     # despite documentation stating that is_file() reports true for symlinks,
     # it appears that is_dir() reports true instead, so we rely on exits().
     if not link_path.exists():