ci: Run sdk and api tests in ci

This adds new makefile targets and configuration to run the tests in the
api and sdk modules. These do not run by default since `go test ./...`
does not cross module boundaries.

CONTRIBUTING.md

@@ -192,4 +192,20 @@ Note that if `max_connections` is set too low, it may result in sporadic test
 failures if a connection cannot be established. In this case, reduce the number
 of concurrent tests via `GOMAXPROCS` or selectively run tests.
 
+### SDK and API tests
+
+Tests for the SDK and API modules can also be run. These do not require a test
+database:
+
+```
+$ make test-api
+$ make test-sdk
+```
+
+Or all of the test can be run with a single target:
+
+```
+$ make test-all
+```
+
 ## [Adding additional field to an existing API (or new API)](internal/adding-a-new-field-readme.md)