refactor: move app.json script execution into it's own plugin

Rather than have this live in 00_dokku-standard, move it out so that it may start to support various other features around the app.json manifest.

tests/unit/30_core_1.bats

@@ -180,24 +180,3 @@ EOF
   echo "status: $status"
   assert_output "3001/udp 3000/tcp 3003"
 }
-
-@test "(core) app.json scripts" {
-  deploy_app
-
-  run /bin/bash -c "dokku run $TEST_APP ls /app/prebuild.test"
-  echo "output: $output"
-  echo "status: $status"
-  assert_failure
-
-  run /bin/bash -c "dokku run $TEST_APP ls /app/predeploy.test"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-
-  CID=$(docker ps -a -q  -f "ancestor=dokku/${TEST_APP}" -f "label=dokku_phase_script=postdeploy")
-  IMAGE_ID=$(docker commit $CID dokku-test/${TEST_APP})
-  run /bin/bash -c "docker run -ti $IMAGE_ID ls /app/postdeploy.test"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-}

tests/unit/40_app-json.bats

@@ -0,0 +1,38 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  global_setup
+  create_app
+  DOCKERFILE="$BATS_TMPDIR/Dockerfile"
+}
+
+teardown() {
+  rm -rf /home/dokku/$TEST_APP/tls
+  destroy_app
+  dokku config:unset --global DOKKU_RM_CONTAINER
+  rm -f "$DOCKERFILE"
+  global_teardown
+}
+
+@test "(app-json) app.json scripts" {
+  deploy_app
+
+  run /bin/bash -c "dokku run $TEST_APP ls /app/prebuild.test"
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+
+  run /bin/bash -c "dokku run $TEST_APP ls /app/predeploy.test"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  CID=$(docker ps -a -q  -f "ancestor=dokku/${TEST_APP}" -f "label=dokku_phase_script=postdeploy")
+  IMAGE_ID=$(docker commit $CID dokku-test/${TEST_APP})
+  run /bin/bash -c "docker run -ti $IMAGE_ID ls /app/postdeploy.test"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+}