fix(team): do not allow leaving exernal teams

frontend/src/modelTypes/ITeam.ts

@@ -9,7 +9,7 @@ export interface ITeam extends IAbstract {
 	description: string
 	members: ITeamMember[]
 	right: Right
-	oidcId: string
+	externalId: string
 	isPublic: boolean
 
 	createdBy: IUser

frontend/src/models/team.ts

@@ -13,7 +13,7 @@ export default class TeamModel extends AbstractModel<ITeam> implements ITeam {
 	description = ''
 	members: ITeamMember[] = []
 	right: Right = RIGHTS.READ
-	oidcId = ''
+	externalId = ''
 	isPublic: boolean = false
 
 	createdBy: IUser = {} // FIXME: seems wrong

frontend/src/views/teams/EditTeam.vue

@@ -194,7 +194,7 @@
 		</Card>
 
 		<x-button
-			v-if="team && !team.oidcId"
+			v-if="team && !team.externalId"
 			class="is-fullwidth is-danger"
 			@click="showLeaveModal = true"
 		>

pkg/models/error.go

@@ -1366,6 +1366,26 @@ func (err ErrOIDCTeamsDoNotExistForUser) HTTPError() web.HTTPError {
 	}
 }
 
+// ErrCannotRemoveUserFromExternalTeam represents an error where an oidcTeam does not exist for the user
+type ErrCannotRemoveUserFromExternalTeam struct {
+	TeamID int64
+}
+
+func (err ErrCannotRemoveUserFromExternalTeam) Error() string {
+	return fmt.Sprintf("Users cannot be removed from an external team [Team ID: %d]", err.TeamID)
+}
+
+const ErrCodeCannotLeaveExternalTeam = 6010
+
+// HTTPError holds the http error description
+func (err ErrCannotRemoveUserFromExternalTeam) HTTPError() web.HTTPError {
+	return web.HTTPError{
+		HTTPCode: http.StatusPreconditionFailed,
+		Code:     ErrCodeCannotLeaveExternalTeam,
+		Message:  "Users cannot be removed from an external team.",
+	}
+}
+
 // ====================
 // User <-> Project errors
 // ====================

pkg/models/team_members.go

@@ -20,6 +20,7 @@ import (
 	"code.vikunja.io/api/pkg/events"
 	user2 "code.vikunja.io/api/pkg/user"
 	"code.vikunja.io/api/pkg/web"
+
 	"xorm.io/xorm"
 )
 
@@ -89,6 +90,15 @@ func (tm *TeamMember) Create(s *xorm.Session, a web.Auth) (err error) {
 // @Router /teams/{id}/members/{username} [delete]
 func (tm *TeamMember) Delete(s *xorm.Session, _ web.Auth) (err error) {
 
+	t, err := GetTeamByID(s, tm.TeamID)
+	if err != nil {
+		return err
+	}
+
+	if t.ExternalID != "" {
+		return ErrCannotRemoveUserFromExternalTeam{tm.TeamID}
+	}
+
 	total, err := s.Where("team_id = ?", tm.TeamID).Count(&TeamMember{})
 	if err != nil {
 		return