refactor: Extract Invitation routes to InvitationController (no-changelog) (#7726)

This PR:

- Creates `InvitationController`
- Moves `POST /users` to `POST /invitations` and move related test to
`invitations.api.tests`
- Moves `POST /users/:id` to `POST /invitations/:id/accept` and move
related test to `invitations.api.tests`
- Adjusts FE to use new endpoints
- Moves all the invitation logic to the `UserService`

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Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/cli/src/requests.ts

@@ -295,6 +295,11 @@ export declare namespace PasswordResetRequest {
 export declare namespace UserRequest {
 	export type Invite = AuthenticatedRequest<{}, {}, Array<{ email: string }>>;
 
+	export type InviteResponse = {
+		user: { id: string; email: string; inviteAcceptUrl?: string; emailSent: boolean };
+		error?: string;
+	};
+
 	export type ResolveSignUp = AuthlessRequest<
 		{},
 		{},