feat: new "Subsonic Minimal Clients" configuration option (#4850)

* Add `.editorconfig` file

Hints to users how to properly indent Go files (my setup was defaulting
to 2 spaces).

* Add Subsonic API minimal config option

This will allow users to specify clients which can operate with or need
the minimum required fields as per the [SubSonic API
spec](https://subsonic.org/pages/api.jsp).

* Return only required fields for Child Objects

For a minimal client, only return the required fields for Child Objects.

* Return only required fields for Playlist objects

* refactor: simplify client list checks and improve playlist response handling

Signed-off-by: Deluan <deluan@navidrome.org>

* test: add unit tests for client list checks and playlist building logic

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: revert Child.IsVideo and Playlist.Public fields from pointer to boolean, and add omitempty to XML tag

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>
Co-authored-by: Deluan Quintão <deluan@navidrome.org>

server/subsonic/responses/.snapshots/Responses Directory with data should match .JSON

@@ -9,8 +9,7 @@
       {
         "id": "1",
         "isDir": false,
-        "title": "title",
-        "isVideo": false
+        "title": "title"
       }
     ],
     "id": "1",