Cf. support request 2829
Provide a property
JiraService in order to customize the API path. This is necessary if for instance Jira is not installed at the root of the web server. For user convenience, the API URL is automatically built from the Project URL using the same logic as before, so that it shouldn't be necessary for users to actually enter the API URL in most cases.
api_version property which seems redundant with the API URL. A DB migration
api_version and initializes the API URL from
api_version using the same logic as before for a seamless transition.