Make all api fields snake_case (#105)

Change all snake/camelCase mix and match to camelCase everywhere

Fix conversion to not interfer with service interceptors

Add dynamic conversion between camelCase and snake_case to services

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/105

src/models/labelTask.js

@@ -5,7 +5,7 @@ export default class LabelTask extends AbstractModel {
 		return {
 			id: 0,
 			taskID: 0,
-			label_id: 0,
+			labelId: 0,
 		}
 	}
 }