fix(projection): remove users with factors (#9877)

# Which Problems Are Solved

When users are removed, their auth factors stay in the projection. This
data inconsistency is visible if a removed user is recreated with the
same ID. In such a case, the login UI and the query API methods show the
removed users auth methods. This is unexpected behavior.

The old users auth methods are not usable to log in and they are not
found by the command side. This is expected behavior.

# How the Problems Are Solved

The auth factors projection reduces the user removed event by deleting
all factors.

# Additional Context

- Reported by support request
- requires backport to 2.x and 3.x

internal/query/projection/user_auth_method.go

@@ -125,6 +125,10 @@ func (p *userAuthMethodProjection) Reducers() []handler.AggregateReducer {
 					Event:  user.HumanOTPEmailRemovedType,
 					Reduce: p.reduceRemoveAuthMethod,
 				},
+				{
+					Event:  user.UserRemovedType,
+					Reduce: p.reduceUserRemoved,
+				},
 			},
 		},
 		{
@@ -311,3 +315,18 @@ func (p *userAuthMethodProjection) reduceOwnerRemoved(event eventstore.Event) (*
 		},
 	), nil
 }
+
+func (p *userAuthMethodProjection) reduceUserRemoved(event eventstore.Event) (*handler.Statement, error) {
+	e, ok := event.(*user.UserRemovedEvent)
+	if !ok {
+		return nil, zerrors.ThrowInvalidArgumentf(nil, "PROJE-FwDZ8", "reduce.wrong.event.type %s", user.UserRemovedType)
+	}
+	return handler.NewDeleteStatement(
+		e,
+		[]handler.Condition{
+			handler.NewCond(UserAuthMethodInstanceIDCol, e.Aggregate().InstanceID),
+			handler.NewCond(UserAuthMethodResourceOwnerCol, e.Aggregate().ResourceOwner),
+			handler.NewCond(UserAuthMethodUserIDCol, e.Aggregate().ID),
+		},
+	), nil
+}

internal/query/projection/user_auth_method_test.go

@@ -528,6 +528,34 @@ func TestUserAuthMethodProjection_reduces(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:   "reduceUserRemoved",
+			reduce: (&userAuthMethodProjection{}).reduceUserRemoved,
+			args: args{
+				event: getEvent(
+					testEvent(
+						user.UserRemovedType,
+						user.AggregateType,
+						nil,
+					), user.UserRemovedEventMapper),
+			},
+			want: wantReduce{
+				aggregateType: eventstore.AggregateType("user"),
+				sequence:      15,
+				executer: &testExecuter{
+					executions: []execution{
+						{
+							expectedStmt: "DELETE FROM projections.user_auth_methods5 WHERE (instance_id = $1) AND (resource_owner = $2) AND (user_id = $3)",
+							expectedArgs: []interface{}{
+								"instance-id",
+								"ro-id",
+								"agg-id",
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name:   "org reduceOwnerRemoved",
 			reduce: (&userAuthMethodProjection{}).reduceOwnerRemoved,