feat: add `available_cpu` variable

Closes #14

See merge request !17

Add `available_cpu` variable for specifying the number of CPUs to allocate to
the Cloud Function.

Add validation checks for the variables `available_cpu`, `available_memory_mb`
and `timeout`.

Closes #14

update CI templates versions

See merge request !16

chore: bump secret manager version number

See merge request !15

fix: ignore changes to docker repository

See merge request !14

Cloud Functions creates a docker repository for us when the function is
created. It's non-trivial to get that name but ignore changes to the
`docker_repository` argument so that we don't get a perma-diff.

feat: enable setting environment variables on the function

See merge request !13

The CI job was failing to install node. Disable temporarily to enable CI
pipelines to pass.

The use of coalesce() failed because both arguments are evaluated. When
there is no script service account, the expression will error because
the script_service_account tuple is empty.

Use the ?: operator which short-circuits evaluation.

It is more convenient to set non-secret information via environment
variables. Expose this functionality.

Move to using Cloud Functions gen 2

Closes #11

See merge request !12

Convert to using Gen 2 runtimes. For most situations this should be a
transparent change but since the runtime _has_ changed and there are
some subtleties around this, mark this as a breaking change. If nothing
else this will cause a removal of the original function and a creation
of a new one along with a change to the schema of the `function` output.

Port the pre-commit jobs, CI jobs, terraform-docs and release it
configuration from the GCP CLoud Run app module.

This involved some automated and some manual fixups to files to appease
the tflint and trivy gods. In particular we needed to add a type
annotation to the `service_account` variable, change the
`service_account` output to match, rename the CHANGELOG file
and re-structure the README to be terraform-docs friendly.

Since the types of the `service_account` variable and output have
changed, mark this as a breaking feature.

feat(alerting): Add failure alerts to catch explicit failures during invocation.

Closes #10

See merge request !11

chore: suppress one of issues in kics report

Closes #8

See merge request !10

feat: Enable versioning for source bucket

Closes #7

See merge request !9

feat: add alert_notification_channels variable

See merge request !8

ci: publish to GitLab Terraform registry when tagged with valid semver

Closes #6

See merge request !7

Update versions.tf

Closes #5

See merge request !6

chore: allow google provider v4

Closes #4

See merge request !5

- archive and random providers defined in required_providers.
- google-beta removed as not being used in module.

Add var for specifying service account (v2)

Closes #2

See merge request !4