Sqlx Cli: Added force flag to drop database for postgres (#2873)

* Updated ahash so it can compile on mac

* Updated MigrateDatabase Trait + related functions

* Postgres force drop database flag impl

* Update migrate.rs

* Reverted MigrateDatabase Trait

* Update migrate.rs

* Update migrate.rs

* Added force drop database fn impl

* Add Migrate Error

* Fixed changed function name

sqlx-postgres/src/migrate.rs

@@ -85,6 +85,30 @@ impl MigrateDatabase for Postgres {
             Ok(())
         })
     }
+
+    fn force_drop_database(url: &str) -> BoxFuture<'_, Result<(), Error>> {
+        Box::pin(async move {
+            let (options, database) = parse_for_maintenance(url)?;
+            let mut conn = options.connect().await?;
+
+            let row: (String,) = query_as("SELECT current_setting('server_version_num')")
+                .fetch_one(&mut conn)
+                .await?;
+
+            let version = row.0.parse::<i32>().unwrap();
+
+            let pid_type = if version >= 90200 { "pid" } else { "procpid" };
+
+            conn.execute(&*format!(
+                "SELECT pg_terminate_backend(pg_stat_activity.{pid_type}) FROM pg_stat_activity \
+                 WHERE pg_stat_activity.datname = {} AND {pid_type} <> pg_backend_pid()",
+                database.replace('"', "\"\""),
+            ))
+            .await?;
+
+            Self::drop_database(url).await
+        })
+    }
 }
 
 impl Migrate for PgConnection {