Fix dependency caching in Docker image build

[zsusswein]

In #41, I add a dependency on the tidybayes package. This is causing the Docker image build to fail because the dependency can't be found.

I think this is an issue with the cache hit? The dependency is successfully updated in the package manifest, so the base "dependency" image should have been refreshed.

As a separate but related question, should this action be running in the PR? Is the idea to have the PR image also in ACR and linked to a pool for testing? Or for running tests in GHA in the built image? If I'm reading this action correctly, it's updating "latest" in ACR off this in-development PR which is perhaps not what we want?

@jkislin -- can you take a look at this?

[gvegayon]

For reference (may not be the solution, but still adding it): we could have workflows calling each other. A caller workflow (e.g., R CMD check) could explicitly call the Dockerimage builder workflow. Here is a link with information about it https://docs.github.com/en/actions/sharing-automations/reusing-workflows#creating-a-reusable-workflow.

[gvegayon]

OK, the resuable workflows are fancy, but too much for this time. We are doing the following (after talking to @zsusswein):

1. Merge workflow 1 into workflow 2.
2. Remove the path condition for triggering the workflow 1 (this is actually solved by step 1).
3. Use the Pr number as the single tag for the image. The tag will change to latest only on merge to main.

I'm branching off main to work on this solution.