chore(deps): update Terraform `google` provider to `>= v5`

See merge request !23

For terraform modules we generally should only ever specify *minimum*
versions. From the docs[1]:

> Reusable modules should constrain only their minimum allowed versions
> of Terraform and providers, such as >= 0.12.0. This helps avoid known
> incompatibilities, while allowing the user of the module flexibility
> to upgrade to newer versions of Terraform without altering the module.

[1] https://developer.hashicorp.com/terraform/language/expressions/
  version-constraints#best-practices

Resolve "Enable specifying monitoring_scoping_project"

Closes #13

See merge request !22

chore(deps): update dependency uis/devops/continuous-delivery/ci-templates to v4.5.0

See merge request !21

See merge request !20

feat: add `schedule_retry_config` variable

Closes #15

See merge request !18

Add `schedule_retry_config` variable that controls the configuration used to
retry a scheduled job that does not complete successfully. It corresponds to
the `retry_config` argument of the `google_cloud_scheduler_job` resource.

Closes #15

feat: add `paused` variable for pausing/unpausing the schedule

Closes #16

See merge request !19

Closes #16

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