fix: consistent permission check on user v2 (#8807)

# Which Problems Are Solved

Some user v2 API calls checked for permission only on the user itself.

# How the Problems Are Solved

Consistent check for permissions on user v2 API.

# Additional Changes

None

# Additional Context

Closes #7944

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/api/grpc/user/v2beta/integration_test/passkey_test.go

@@ -92,15 +92,30 @@ func TestServer_RegisterPasskey(t *testing.T) {
 			wantErr: true,
 		},
 		{
-			name: "user mismatch",
+			name: "user no permission",
 			args: args{
-				ctx: CTX,
+				ctx: UserCTX,
 				req: &user.RegisterPasskeyRequest{
 					UserId: userID,
 				},
 			},
 			wantErr: true,
 		},
+		{
+			name: "user permission",
+			args: args{
+				ctx: IamCTX,
+				req: &user.RegisterPasskeyRequest{
+					UserId: userID,
+				},
+			},
+			want: &user.RegisterPasskeyResponse{
+				Details: &object.Details{
+					ChangeDate:    timestamppb.Now(),
+					ResourceOwner: Instance.DefaultOrg.Id,
+				},
+			},
+		},
 		{
 			name: "user setting its own passkey",
 			args: args{