Integration Test for Onchain Transactions

[owenkellogg]

Earlier today GET /api/v1/content/{txid} began returning a 400 error for onchain.sv transactions (and ostensibly other non BMAP transactions).

This could have been prevented by writing an integration test that exercises the API (in-memory locally in the test environment) by providing valid onchain.sv transactions several times and asserting a consistent 200 response.