refactor: move general interface to interfaces directory

This commit relocates the 'general.interface.ts' file from the 'services' directory to the 'interfaces' directory. This structural change is meant to streamline the organization of the code base.

src/interfaces/general.interface.ts

@@ -0,0 +1,13 @@
+export interface IStandardisedReturn<T> {
+	state: EReturnState;
+	message?: string;
+	resolved?: T;
+}
+
+export enum EReturnState {
+	unauthorized = 0,
+	clientError = 1,
+	serverError = 2,
+	done = 3,
+	queued = 4,
+}