Enable/disable owner and repo projects independently (#28805)

Part of #23318 

Add menu in repo settings to allow for repo admin to decide not just if
projects are enabled or disabled per repo, but also which kind of
projects (repo-level/owner-level) are enabled. If repo projects
disabled, don't show the projects tab.


![grafik](https://github.com/go-gitea/gitea/assets/47871822/b9b43fb4-824b-47f9-b8e2-12004313647c)

---------

Co-authored-by: delvh <dev.lh@web.de>

models/fixtures/repo_unit.yml

@@ -520,6 +520,7 @@
   id: 75
   repo_id: 1
   type: 8
+  config: "{\"ProjectsMode\":\"all\"}"
   created_unix: 946684810
 
 -
@@ -650,12 +651,6 @@
   type: 2
   created_unix: 946684810
 
--
-  id: 98
-  repo_id: 1
-  type: 8
-  created_unix: 946684810
-
 -
   id: 99
   repo_id: 1

models/repo/repo.go

@@ -411,6 +411,11 @@ func (repo *Repository) MustGetUnit(ctx context.Context, tp unit.Type) *RepoUnit
 			Type:   tp,
 			Config: new(ActionsConfig),
 		}
+	} else if tp == unit.TypeProjects {
+		return &RepoUnit{
+			Type:   tp,
+			Config: new(ProjectsConfig),
+		}
 	}
 
 	return &RepoUnit{

models/repo/repo_unit.go

@@ -202,6 +202,53 @@ func (cfg *ActionsConfig) ToDB() ([]byte, error) {
 	return json.Marshal(cfg)
 }
 
+// ProjectsMode represents the projects enabled for a repository
+type ProjectsMode string
+
+const (
+	// ProjectsModeRepo allows only repo-level projects
+	ProjectsModeRepo ProjectsMode = "repo"
+	// ProjectsModeOwner allows only owner-level projects
+	ProjectsModeOwner ProjectsMode = "owner"
+	// ProjectsModeAll allows both kinds of projects
+	ProjectsModeAll ProjectsMode = "all"
+	// ProjectsModeNone doesn't allow projects
+	ProjectsModeNone ProjectsMode = "none"
+)
+
+// ProjectsConfig describes projects config
+type ProjectsConfig struct {
+	ProjectsMode ProjectsMode
+}
+
+// FromDB fills up a ProjectsConfig from serialized format.
+func (cfg *ProjectsConfig) FromDB(bs []byte) error {
+	return json.UnmarshalHandleDoubleEncode(bs, &cfg)
+}
+
+// ToDB exports a ProjectsConfig to a serialized format.
+func (cfg *ProjectsConfig) ToDB() ([]byte, error) {
+	return json.Marshal(cfg)
+}
+
+func (cfg *ProjectsConfig) GetProjectsMode() ProjectsMode {
+	if cfg.ProjectsMode != "" {
+		return cfg.ProjectsMode
+	}
+
+	return ProjectsModeNone
+}
+
+func (cfg *ProjectsConfig) IsProjectsAllowed(m ProjectsMode) bool {
+	projectsMode := cfg.GetProjectsMode()
+
+	if m == ProjectsModeNone {
+		return true
+	}
+
+	return projectsMode == m || projectsMode == ProjectsModeAll
+}
+
 // BeforeSet is invoked from XORM before setting the value of a field of this object.
 func (r *RepoUnit) BeforeSet(colName string, val xorm.Cell) {
 	switch colName {
@@ -217,7 +264,9 @@ func (r *RepoUnit) BeforeSet(colName string, val xorm.Cell) {
 			r.Config = new(IssuesConfig)
 		case unit.TypeActions:
 			r.Config = new(ActionsConfig)
-		case unit.TypeCode, unit.TypeReleases, unit.TypeWiki, unit.TypeProjects, unit.TypePackages:
+		case unit.TypeProjects:
+			r.Config = new(ProjectsConfig)
+		case unit.TypeCode, unit.TypeReleases, unit.TypeWiki, unit.TypePackages:
 			fallthrough
 		default:
 			r.Config = new(UnitConfig)
@@ -265,6 +314,11 @@ func (r *RepoUnit) ActionsConfig() *ActionsConfig {
 	return r.Config.(*ActionsConfig)
 }
 
+// ProjectsConfig returns config for unit.ProjectsConfig
+func (r *RepoUnit) ProjectsConfig() *ProjectsConfig {
+	return r.Config.(*ProjectsConfig)
+}
+
 func getUnitsByRepoID(ctx context.Context, repoID int64) (units []*RepoUnit, err error) {
 	var tmpUnits []*RepoUnit
 	if err := db.GetEngine(ctx).Where("repo_id = ?", repoID).Find(&tmpUnits); err != nil {