MM-14753: Verifies that user can join teams and channels in spite of group constraints. (#10529)

* MM-147753: Verifies that users are allowed to be members of a team or a channel, based on group constraints, prior to allowing the API to add them.

* MM-14753: Allow methods to return meaningful results for deleted teams or channels.

* MM-14753: Renames methods to differentiate from permissions and other team and channel restrictions.

* MM-14753: Only check if users are team/channel members if team/channel is group constrained.

* MM-14753: Updates test function names.

* MM-14753: Changes a few method signatures.

* MM-14753: Small refactor and adds missing returns.

* MM-14753: Changes method names from Get* to Filter* name prefixes.

* MM-14753: Renames error variables.

* MM-14753: Updates method names for consistency with join table names.

* MM-14753: Adds case for non AppError return.

* Update i18n/en.json

api4/apitestlib.go

@@ -44,6 +44,7 @@ type TestHelper struct {
 	BasicDeletedChannel *model.Channel
 	BasicChannel2       *model.Channel
 	BasicPost           *model.Post
+	Group               *model.Group
 
 	SystemAdminClient *model.Client4
 	SystemAdminUser   *model.User
@@ -210,6 +211,7 @@ func (me *TestHelper) InitBasic() *TestHelper {
 	me.App.UpdateUserRoles(me.BasicUser.Id, model.SYSTEM_USER_ROLE_ID, false)
 	me.Client.DeleteChannel(me.BasicDeletedChannel.Id)
 	me.LoginBasic()
+	me.Group = me.CreateGroup()
 
 	return me
 }
@@ -509,6 +511,24 @@ func (me *TestHelper) GenerateTestEmail() string {
 	return strings.ToLower(model.NewId() + "@dockerhost")
 }
 
+func (me *TestHelper) CreateGroup() *model.Group {
+	id := model.NewId()
+	group := &model.Group{
+		Name:        "n-" + id,
+		DisplayName: "dn_" + id,
+		Source:      model.GroupSourceLdap,
+		RemoteId:    "ri_" + id,
+	}
+
+	utils.DisableDebugLogForTest()
+	group, err := me.App.CreateGroup(group)
+	if err != nil {
+		panic(err)
+	}
+	utils.EnableDebugLogForTest()
+	return group
+}
+
 func GenerateTestUsername() string {
 	return "fakeuser" + model.NewRandomString(10)
 }