Extends management user and group structure (#1268)

* extends user and group structure by introducing fields for issued and integration references

* Add integration checks to group management to prevent groups added by integration.

* Add integration checks to user management to prevent deleting user added by integration.

* Fix broken user update tests

* Initialize all user fields for testing

* Change a serializer option to embedded for IntegrationReference in user and group models

* Add issued field to user api response

* Add IntegrationReference to Group in update groups handler

* Set the default issued field for users in file store

management/server/group.go

@@ -34,6 +34,8 @@ type Group struct {
 
 	// Peers list of the group
 	Peers []string `gorm:"serializer:json"`
+
+	IntegrationReference IntegrationReference `gorm:"embedded;embeddedPrefix:integration_ref_"`
 }
 
 // EventMeta returns activity event meta related to the group
@@ -160,6 +162,11 @@ func (am *DefaultAccountManager) DeleteGroup(accountId, userId, groupID string)
 		return nil
 	}
 
+	// check integration link
+	if g.Issued == GroupIssuedIntegration {
+		return &GroupLinkError{GroupIssuedIntegration, g.IntegrationReference.String()}
+	}
+
 	// check route links
 	for _, r := range account.Routes {
 		for _, g := range r.Groups {