Support setting use_featureinfo_custom_template through rest api

[pchevali]

Is your feature request related to a problem? Please describe.
It seems that to change the "use_featureinfo_custom_template" flag only metadata upload is supported.
Although we can set the "featureinfo_custom_template" through rest, and we see that it is stored in the database. A patch request with "use_featureinfo_custom_template": True will not be stored.

Describe the solution you'd like
Support setting the "use_featureinfo_custom_template" flag through rest api (GET, POST, PATCH)

Describe alternatives you've considered
Using the metadata post request as in the metadata setting page. However is not as convenient as the patch request.