Add core storage plugin to manage docker bind mounts [ci skip]

tests/unit/20_storage.bats

@@ -0,0 +1,40 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  create_app
+}
+
+teardown() {
+  destroy_app
+}
+
+@test "(storage) storage:mount, storage:list, storage:umount" {
+  run /bin/bash -c "dokku storage:mount $TEST_APP /tmp/mount:/mount"
+  echo "output: "$output
+  echo "status: "$status
+  assert_success
+  run /bin/bash -c "dokku storage:list $TEST_APP | grep -qe '^\s*/tmp/mount:/mount'"
+  echo "output: "$output
+  echo "status: "$status
+  assert_success
+  run /bin/bash -c "dokku storage:mount $TEST_APP /tmp/mount:/mount"
+  echo "output: "$output
+  echo "status: "$status
+  assert_output "Mount path already exists."
+  assert_failure
+  run /bin/bash -c "dokku storage:unmount $TEST_APP /tmp/mount:/mount"
+  echo "output: "$output
+  echo "status: "$status
+  assert_success
+  run /bin/bash -c "dokku storage:list $TEST_APP | grep -vqe '^\s*/tmp/mount:/mount'"
+  echo "output: "$output
+  echo "status: "$status
+  assert_success
+  run /bin/bash -c "dokku storage:unmount $TEST_APP /tmp/mount:/mount"
+  echo "output: "$output
+  echo "status: "$status
+  assert_output "Mount path does not exist."
+  assert_failure
+}