We found out in #9953 that, appparently, loading the OpenAPI file was
taking abut a 5% of the Zulip server startup time.
Since in many cases (especially in development) having the file loaded
won't be necessary at all, we read it on the first time data from the
OpenAPI spec is needed.
Tweaked by tabbott to add a test.
Automatically detect if the OpenAPI spec file has been modified since
the last time it was loaded into memory, and if it has, automatically
reload it to have the latest version.
This feature is designed with development environments in mind. The main
benefit is being able to see the changes made to the OpenAPI document
without needing to restart the development server, which is tedious and
slows the documentation workflow down.
Yago González