Support for publishing SQL schema from scratch, and publishing from a branch

[inahga]

Fixes #1735.

Appropriately handle the case where we're starting a new release and need to have the migrations directory created. The force flag is not required for this operation (nor should it IMO).

I also fix the job to allow us deploying from a branch, in which case the directory will just be the branch name. This is mainly for testing this PR but I can see it being useful in niche circumstances.

To cleanly accomplish this I replace gcloud with rclone, for a few reasons:

• rclone is a stable interface, gcloud alpha is not.
• rclone has more predictable and favorable semantics, i.e. we don't need any special handling for the case where the remote migrations directory doesn't exist.
• gcloud alpha doesn't have a directory existence test function, nor does it provide any sensible way of parsing the kind of error that occurs. So to ignore a missing remote directory we have to do || true or do if grep "not found" <<<$OUTPUT, neither of which are very good solutions.

Expand for details on the testing I did for this:

• Setting up schema from scratch https://github.com/divviup/janus/actions/runs/5906546433/job/16022784957.

  🐧 rclone ls --verbose gs:/janus-artifacts-sql-schemas | grep inahga/test
       1734 inahga/test-1735/db/00000000000001_initial_schema.down.sql
      24634 inahga/test-1735/db/00000000000001_initial_schema.up.sql
  

• Add new migration to existing schema https://github.com/divviup/janus/actions/runs/5906561538/job/16022835739

  🐧 rclone ls --verbose gs:/janus-artifacts-sql-schemas | grep inahga/test
       1734 inahga/test-1735/db/00000000000001_initial_schema.down.sql
      24634 inahga/test-1735/db/00000000000001_initial_schema.up.sql
          4 inahga/test-1735/db/00000000000002_foo.down.sql
          4 inahga/test-1735/db/00000000000002_foo.up.sql
  

• Attempt modifying existing schema, fails as expected. https://github.com/divviup/janus/actions/runs/5906574446/job/1602287765. (output was same as above).
• I assert that I know what I'm doing, and force the migration to continue anyway with the force flag. https://github.com/divviup/janus/actions/runs/5906628503/job/16023031038

  🐧 rclone ls --verbose gs:/janus-artifacts-sql-schemas | grep inahga/test
       1734 inahga/test-1735/db/00000000000001_initial_schema.down.sql
          4 inahga/test-1735/db/00000000000001_initial_schema.up.sql
          4 inahga/test-1735/db/00000000000002_foo.down.sql
          4 inahga/test-1735/db/00000000000002_foo.up.sql
  

• Isolation test that asserts the version parsing changes haven't broken anything:

  🐧 cat test.sh
  #!/usr/bin/env bash
  
  if grep -P "^refs/tags/" <<<"$GITHUB_REF" >/dev/null; then
          VERSION=${GITHUB_REF/refs\/tags\//}
          MINOR_VERSION="$(echo "$VERSION" | awk -F'.' '{if (NF != 3) {exit 1}; printf "%s.%s", $1, $2}')"
          echo "version=$MINOR_VERSION"
  elif grep -P "^refs/heads/" <<<"$GITHUB_REF" >/dev/null; then
          BRANCH=${GITHUB_REF/refs\/heads\//}
          echo "version=$BRANCH"
  else
          echo "Unable to parse version information"
          exit 1
  fi
  
  🐧 GITHUB_REF=refs/tags/0.1.2 ./test.sh
  version=0.1
  🐧 GITHUB_REF=refs/tags/0.subscriber-01.2 ./test.sh
  version=0.subscriber-01
  🐧 GITHUB_REF=refs/heads/inahga/test ./test.sh
  version=inahga/test
  🐧 GITHUB_REF=refs/heads/inahga/test/foo/bar ./test.sh
  version=inahga/test/foo/bar
  🐧 GITHUB_REF=refs/heads/branch ./test.sh
  version=branch
  🐧 GITHUB_REF=idk/wtf ./test.sh
  Unable to parse version information