feat: Improve oauth redirect (#303)

* fix: redirects after oauth can potentially misalign with server's actually hostname

* feat: remove `RedirectURL` from oauth config, as it should checked by provider rather than client

* feat: align oauth endpoint with the hostname in requests

docs/admin/admin_swagger.json

@@ -5562,8 +5562,7 @@
             "required": [
                 "client_id",
                 "client_secret",
-                "oauth_type",
-                "redirect_url"
+                "oauth_type"
             ],
             "properties": {
                 "auto_register": {
@@ -5593,9 +5592,6 @@
                 "pkce_method": {
                     "type": "string"
                 },
-                "redirect_url": {
-                    "type": "string"
-                },
                 "scopes": {
                     "type": "string"
                 }
@@ -6289,9 +6285,6 @@
                 "pkce_method": {
                     "type": "string"
                 },
-                "redirect_url": {
-                    "type": "string"
-                },
                 "scopes": {
                     "type": "string"
                 },
@@ -6595,4 +6588,4 @@
             "in": "header"
         }
     }
-}
+}