Add Org user revoke feature

This PR adds a the new v2022.8.x revoke feature which allows an
organization owner or admin to revoke access for one or more users.

This PR also fixes several permissions and policy checks which were faulty.

- Modified some functions to use DB Count features instead of iter/count aftwards.
- Rearanged some if statements (faster matching or just one if instead of nested if's)
- Added and fixed several policy checks where needed
- Some small updates on some response models
- Made some functions require an enum instead of an i32

src/api/core/sends.rs

@@ -70,8 +70,9 @@ struct SendData {
 /// controls this policy globally.
 async fn enforce_disable_send_policy(headers: &Headers, conn: &DbConn) -> EmptyResult {
     let user_uuid = &headers.user.uuid;
-    let policy_type = OrgPolicyType::DisableSend;
-    if !CONFIG.sends_allowed() || OrgPolicy::is_applicable_to_user(user_uuid, policy_type, conn).await {
+    if !CONFIG.sends_allowed()
+        || OrgPolicy::is_applicable_to_user(user_uuid, OrgPolicyType::DisableSend, None, conn).await
+    {
         err!("Due to an Enterprise Policy, you are only able to delete an existing Send.")
     }
     Ok(())