Build API form generator service

[dleard]

Blocked on #270

Once the work in #254 is complete & we have the database structures needed to support dynamic form generation from configs, we can build the API endpoint/service that will build these forms dynamically on request.

As a developer I want an API route/service for form generation So that when it is called from an emission form it returns a generated schema

As a developer When I call the API route with the general stationary combustion activity/source types It returns the correctly generated forms for those inputs

AC:

• [x] The reporting app in django has an api router
• [x] A route & service exists for dynamic form generation (/api/reporting/generate-json-schema?)
• [x] The service pulls a base schema based on the activity-sourceType pair from the base_schema table
• [x] The service dynamically adds the fields from the reporting_fields table related to the gasType/methodology selections
• [x] The service returns a json schema made up of the base schema & dynamic fields
• [ ] ~The api route is protected so only logged in users can hit it~ let's do this in #253 to make it easier to start development on that card without protections in place
• [ ] pytests for the service

[dleard]

Pulling this out of 'in progress' for now in favour of #270 as our understanding of what is required to build the forms has changed. Once #270 is in, some of the work already done here will provide the basis for building the form generator service in a way that is modified to handle the new database models. @pbastia @patriciarussellCAS