add template folder CRUD

* create template folder
* rename template folder
* get list of template folders for service (not nested/presented in any
  particular way)
* delete template folder

Also removed `lazy=dynamic` from the `template_folder.templates`
relationship. lazy=dynamic returns a query object (which you can then
filter further). We just want to return the entire fetched list, at
least for now.

app/template_folder/rest.py

@@ -0,0 +1,84 @@
+from flask import Blueprint, jsonify, request
+from sqlalchemy.exc import IntegrityError
+
+from app.dao.template_folder_dao import (
+    dao_create_template_folder,
+    dao_get_template_folder_by_id,
+    dao_update_template_folder,
+    dao_delete_template_folder
+)
+from app.dao.services_dao import dao_fetch_service_by_id
+from app.errors import register_errors
+from app.models import TemplateFolder
+from app.template_folder.template_folder_schema import (
+    post_create_template_folder_schema,
+    post_rename_template_folder_schema
+)
+from app.schema_validation import validate
+
+template_folder_blueprint = Blueprint(
+    'template_folder',
+    __name__,
+    url_prefix='/service/<uuid:service_id>/template-folder'
+)
+register_errors(template_folder_blueprint)
+
+
+@template_folder_blueprint.errorhandler(IntegrityError)
+def handle_integrity_error(exc):
+    if 'template_folder_parent_id_fkey' in str(exc):
+        return jsonify(result='error', message='parent_id not found'), 400
+
+    raise
+
+
+@template_folder_blueprint.route('', methods=['GET'])
+def get_template_folders_for_service(service_id):
+    service = dao_fetch_service_by_id(service_id)
+
+    template_folders = [o.serialize() for o in service.all_template_folders]
+    return jsonify(template_folders=template_folders)
+
+
+@template_folder_blueprint.route('', methods=['POST'])
+def create_template_folder(service_id):
+    data = request.get_json()
+
+    validate(data, post_create_template_folder_schema)
+
+    template_folder = TemplateFolder(
+        service_id=service_id,
+        name=data['name'].strip(),
+        parent_id=data['parent_id']
+    )
+
+    dao_create_template_folder(template_folder)
+
+    return jsonify(data=template_folder.serialize()), 201
+
+
+@template_folder_blueprint.route('/<uuid:template_folder_id>/rename', methods=['POST'])
+def rename_template_folder(service_id, template_folder_id):
+    data = request.get_json()
+
+    validate(data, post_rename_template_folder_schema)
+
+    template_folder = dao_get_template_folder_by_id(template_folder_id)
+    template_folder.name = data['name']
+
+    dao_update_template_folder(template_folder)
+
+    return jsonify(data=template_folder.serialize()), 200
+
+
+@template_folder_blueprint.route('/<uuid:template_folder_id>', methods=['DELETE'])
+def delete_template_folder(service_id, template_folder_id):
+    template_folder = dao_get_template_folder_by_id(template_folder_id)
+
+    # don't allow deleting if there's anything in the folder (even if it's just more empty subfolders)
+    if template_folder.subfolders or template_folder.templates:
+        return jsonify(result='error', message='Folder is not empty'), 400
+
+    dao_delete_template_folder(template_folder)
+
+    return '', 204