Explicitly auth to apk.cgr.dev (#19)

We have an option for exporting `HTTP_AUTH`, but I'm 90% sure this won't
work with assumed identities unless we explicitly `chainctl auth login`
using the identity and audience first.

Signed-off-by: Matt Moore <mattmoor@chainguard.dev>

Author: mattmoor

action.yaml

@@ -122,6 +122,10 @@ runs:
           echo Unable to assume the identity ${{ env.IDENTITY }}.
           exit 1
         fi
+        if ! chainctl auth login --identity "${{ env.IDENTITY }}" --audience apk.cgr.dev -v=${{ env.VERBOSITY }}; then
+          echo Unable to assume the identity ${{ env.IDENTITY }} for apk.cgr.dev.
+          exit 1
+        fi
         if ! chainctl auth configure-docker --identity "${{ env.IDENTITY }}" -v=${{ env.VERBOSITY }}; then
           echo Unable to register credential helper as ${{ env.IDENTITY }}.
           exit 1