By referencing the template instead of the "initial_uri" (Forms
composer), the backend is able to more precisely identify the correct
HTML file for any given template. It also makes handling of reply
templates much easier.
In addition to a less complex implementation, this simplifies the API as
we no longer need to supply the frontend with URIs for all HTML
variants. We also get increased performance because of the simplified
file search, and by not having to parse reply templates upfront.
This also opens up the possibility of serving a specialized HTML-based
composer for text-only templates in the future, without having to change
the existing frontend.
Some templates references HTML Forms and reply templates located in
adjecent folders, without specifying a relative path. Examples of this
can be found in `MAPPING-GIS FORMS`.
