make oauth client trully optional (#84)

Same old song, after migraiton to packages some optional modules are
being imported globally which lead to making hard dependency

src/ahriman/core/auth/__init__.py

@@ -18,6 +18,3 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 #
 from ahriman.core.auth.auth import Auth
-
-from ahriman.core.auth.mapping import Mapping
-from ahriman.core.auth.oauth import OAuth

src/ahriman/core/auth/auth.py

@@ -78,10 +78,10 @@ class Auth(LazyLogging):
         """
         provider = AuthSettings.from_option(configuration.get("auth", "target", fallback="disabled"))
         if provider == AuthSettings.Configuration:
-            from ahriman.core.auth import Mapping
+            from ahriman.core.auth.mapping import Mapping
             return Mapping(configuration, database)
         if provider == AuthSettings.OAuth:
-            from ahriman.core.auth import OAuth
+            from ahriman.core.auth.oauth import OAuth
             return OAuth(configuration, database)
         return cls(configuration)
 

src/ahriman/core/auth/oauth.py

@@ -21,7 +21,7 @@ import aioauth_client
 
 from typing import Optional, Type
 
-from ahriman.core.auth import Mapping
+from ahriman.core.auth.mapping import Mapping
 from ahriman.core.configuration import Configuration
 from ahriman.core.database import SQLite
 from ahriman.core.exceptions import OptionError

src/ahriman/web/views/user/login.py

@@ -53,7 +53,7 @@ class LoginView(BaseView):
         Examples:
             This request must not be used directly.
         """
-        from ahriman.core.auth import OAuth
+        from ahriman.core.auth.oauth import OAuth
 
         oauth_provider = self.validator
         if not isinstance(oauth_provider, OAuth):  # there is actually property, but mypy does not like it anyway