Federated user activity following: Isolated model changes (#8078)

This PR is part of https://codeberg.org/forgejo/forgejo/pulls/4767

This should not have an outside impact but bring all model changes needed & bring migrations.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8078
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Michael Jerger <michael.jerger@meissa-gmbh.de>
Co-committed-by: Michael Jerger <michael.jerger@meissa-gmbh.de>

models/user/federated_user_follower_test.go

@@ -0,0 +1,27 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package user
+
+import (
+	"testing"
+
+	"forgejo.org/modules/validation"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_FederatedUserFollowerValidation(t *testing.T) {
+	sut := FederatedUserFollower{
+		FollowedUserID:  12,
+		FollowingUserID: 1,
+	}
+	res, err := validation.IsValid(sut)
+	assert.Truef(t, res, "sut should be valid but was %q", err)
+
+	sut = FederatedUserFollower{
+		FollowedUserID: 1,
+	}
+	res, _ = validation.IsValid(sut)
+	assert.False(t, res, "sut should be invalid")
+}