SUGGESTION: Publish a swagger file

Publish a swagger file.

Currently the frontend integration tests test the frontend in isolation and mock all the services in the backend.

This means the mocks need to match what the chainservice provides.

As a stopgap until we have a GraphQL schema or have implemented something like contract driven testing I suggest we publish a swagger file.

The advantage being that the frontend can have a test to download it from the *.net chain service and check that the swagger file matches all the frontend mocks.

if the swaggerfile changes an API in use the frontend tests will break and frontend will need to support the change.

Of course it would be better if the file was generated using automated frameworks but even a hand edited file would work fine so long as folks working on the backend service remember to update it.