feat: Implement oauth2 monitors (#3119)

* [empty commit] pull request for implement oauth2 monitor

* feat: implement oauth2 client credentials flow

* fix: auth methods clarification & error handling

* docs: fix JSdocs types and clarifications

db/patch-monitor-oauth-cc.sql

@@ -0,0 +1,19 @@
+-- You should not modify if this have pushed to Github, unless it does serious wrong with the db.
+BEGIN TRANSACTION;
+
+ALTER TABLE monitor
+    ADD oauth_client_id TEXT default null;
+
+ALTER TABLE monitor
+    ADD oauth_client_secret TEXT default null;
+
+ALTER TABLE monitor
+    ADD oauth_token_url TEXT default null;
+
+ALTER TABLE monitor
+    ADD oauth_scopes TEXT default null;
+
+ALTER TABLE monitor
+    ADD oauth_auth_method TEXT default null;
+
+COMMIT;