Added SQL cloud proxy support guide for postgres dependent services

[priyadarshini-ni]

• This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

The support guide for adding cloud SQL auth proxy container as sidecar has been added to the services which uses postgres namely testmonitor service, dashboardhosts service and dynamic form fields.

Why should this Pull Request be merged?

1. Updated the systemlink-values.yaml to include the sidecar container support. It doesn't restrict the use to just Cloud SQL auth proxy but allows any container addition as a sidecar along with any volumes needed. This approach is inspired by Grafana where we can use a similar approach to add sidecar containers.
2. Dashboardhosts uses the parameters 'extraContainers' and 'extraContainerVolumes' instead of 'sidecars' and 'extraVolumes' as only that is supported by the 3rd party Grafana chart.
3. The support to add annotations to the serviceAccount has also been added. This is required to link the service account with the Google service account which will have the permissions required for Cloud SQL Workload Identity.

What testing has been done?

NA

[SSSantosh18]

Update the similar changes for other services too

[SSSantosh18]

same comments will apply for other services too

[SSSantosh18]

remove the unnecessary white space changes if possible

[prestwick]

I would prefer if these changes be in their own dedicated YAML file within the GCP directory of templates once #237 goes in.

[prestwick]

I need some clarifications of the parameters that need to be supplied (or not) to enable the auth proxy. Essentially I'm looking for understanding to ensure our inline documentation is complete.

[prestwick]

Are uses required to provide a value here? I cannot tell from the reference GCP docs what value to enter here?

[priyadarshini-ni]

The intention of exposing the parameters sidecars and extraVolumes is to enable the users to configure an extra container which runs along with the service pod. This could also be a Cloud SQL auth proxy container.

The reference documentation has been updated to point to the GCP supplemental values file as this has more information on how the required Cloud SQL authentication proxy container can be configured.

[priyadarshini-ni]

I need some clarifications of the parameters that need to be supplied (or not) to enable the auth proxy. Essentially I'm looking for understanding to ensure our inline documentation is complete.

The PR for GCP supplemental values contains more details on the Cloud SQL auth proxy can be configured. The same file can be referenced in the systemlink-values.yaml file once the PR is merged.

[priyadarshini-ni]

I would prefer if these changes be in their own dedicated YAML file within the GCP directory of templates once #237 goes in.

This PR is meant to expose the parameters(sidecards, extraVolumes, extraVolumeMounts and serviceAccount) required to configure sidecar containers for the postgres dependent services.
#237 intends to add CloudSQL auth proxy containers for the postgres services using the above-mentioned parameters. Moving the contents of this PR to a dedicated YAML file might create some duplication. Let us know is we should approach this in any other way.