Fix External ID not set during DC Sync

While working on the fix I realised the location where the `external_id`
is stored was wrong. It was stored in the `users` table, but it actually
should have been stored in the `users_organizations` table.

This will move the column to the right table. It will not move the
values of the `external_id` column, because if there are more
organizations, there is no way to really know which organization it is
linked to. Setups using the Directory Connector can clear the sync
cache, and sync again, that will store all the `external_id` values at
the right location.

Also changed the function to revoke,restore an org-user and set_external_id to return a boolean.
It will state if the value has been changed or not, and if not, we can
prevent a `save` call to the database.

The `users` table is not changed to remove the `external_id` column, thi
to prevent issue when users want to revert back to an earlier version
for some reason. We can do this after a few minor release i think.

Fixes #3777

src/db/models/organization.rs

@@ -31,6 +31,7 @@ db_object! {
         pub status: i32,
         pub atype: i32,
         pub reset_password_key: Option<String>,
+        pub external_id: Option<String>,
     }
 
     #[derive(Identifiable, Queryable, Insertable, AsChangeset)]
@@ -208,19 +209,37 @@ impl UserOrganization {
             status: UserOrgStatus::Accepted as i32,
             atype: UserOrgType::User as i32,
             reset_password_key: None,
+            external_id: None,
         }
     }
 
-    pub fn restore(&mut self) {
+    pub fn restore(&mut self) -> bool {
         if self.status < UserOrgStatus::Accepted as i32 {
             self.status += ACTIVATE_REVOKE_DIFF;
+            return true;
         }
+        false
     }
 
-    pub fn revoke(&mut self) {
+    pub fn revoke(&mut self) -> bool {
         if self.status > UserOrgStatus::Revoked as i32 {
             self.status -= ACTIVATE_REVOKE_DIFF;
+            return true;
         }
+        false
+    }
+
+    pub fn set_external_id(&mut self, external_id: Option<String>) -> bool {
+        //Check if external id is empty. We don't want to have
+        //empty strings in the database
+        if self.external_id != external_id {
+            self.external_id = match external_id {
+                Some(external_id) if !external_id.is_empty() => Some(external_id),
+                _ => None,
+            };
+            return true;
+        }
+        false
     }
 }
 
@@ -434,7 +453,7 @@ impl UserOrganization {
             "UserId": self.user_uuid,
             "Name": user.name,
             "Email": user.email,
-            "ExternalId": user.external_id,
+            "ExternalId": self.external_id,
             "Groups": groups,
             "Collections": collections,
 
@@ -778,6 +797,17 @@ impl UserOrganization {
             .load::<UserOrganizationDb>(conn).expect("Error loading user organizations").from_db()
         }}
     }
+
+    pub async fn find_by_external_id_and_org(ext_id: &str, org_uuid: &str, conn: &mut DbConn) -> Option<Self> {
+        db_run! {conn: {
+            users_organizations::table
+            .filter(
+                users_organizations::external_id.eq(ext_id)
+                .and(users_organizations::org_uuid.eq(org_uuid))
+            )
+            .first::<UserOrganizationDb>(conn).ok().from_db()
+        }}
+    }
 }
 
 impl OrganizationApiKey {