feat: add subcommands to allow app locking and unlocking

Unlocking an app will not stop running deploys, so users may need to clean up. However, it is useful for deploys that fail in unusual ways that cause the lock to stay around.

Closes #2883

plugins/apps/subcommands/unlock

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
+source "$PLUGIN_AVAILABLE_PATH/apps/internal-functions"
+
+apps_unlock_cmd() {
+  declare desc="removes the '.deploy.lock' file from an application's repo"
+  declare cmd="apps:unlock"
+  [[ "$1" == "$cmd" ]] && shift 1
+  declare APP="$1"; verify_app_name "$APP"
+
+  if [[ -f "$DOKKU_ROOT/$APP/.deploy.lock" ]]; then
+  	dokku_log_warn "A deploy may be in progress."
+  	dokku_log_warn "Removing the application lock will not stop in progress deploys."
+  fi
+
+  rm -f "$DOKKU_ROOT/$APP/.deploy.lock" || dokku_log_fail "Unable to remove deploy lock"
+
+  dokku_log_info1 "Deploy lock removed."
+}
+
+apps_unlock_cmd "$@"