[API] add GET /orgs endpoint (#9560)

* introduce `GET /orgs`

* add TEST

* show also other VisibleType's

* update description

* refactor a lot

* SearchUserOptions by default return only public

models/user.go

@@ -1469,7 +1469,7 @@ type SearchUserOptions struct {
 	UID           int64
 	OrderBy       SearchOrderBy
 	Page          int
-	Private       bool  // Include private orgs in search
+	Visible       []structs.VisibleType
 	OwnerID       int64 // id of user for visibility calculation
 	PageSize      int   // Can be smaller than or equal to setting.UI.ExplorePagingNum
 	IsActive      util.OptionalBool
@@ -1492,8 +1492,9 @@ func (opts *SearchUserOptions) toConds() builder.Cond {
 		cond = cond.And(keywordCond)
 	}
 
-	if !opts.Private {
-		// user not logged in and so they won't be allowed to see non-public orgs
+	if len(opts.Visible) > 0 {
+		cond = cond.And(builder.In("visibility", opts.Visible))
+	} else {
 		cond = cond.And(builder.In("visibility", structs.VisibleTypePublic))
 	}