Measure coverage for pkg folder.

We recently moved a fair amount of code under from `internal` to the
`pkg` folder. This fixes our CI configuration to measure coverage for
that package as well.

.mk/test.mk

@@ -5,7 +5,7 @@
 # in future, we may want to parse these from a file instead of hardcoding them
 # in the Makefile
 COVERAGE_EXCLUSIONS="internal/db\|/mock/\|internal/auth/keycloak/client\|internal/proto"
-COVERAGE_PACKAGES=./internal/...
+COVERAGE_PACKAGES=./internal/...,./pkg/...
 
 .PHONY: clean
 clean:: ## clean up environment