feat(server options): allow connection timeouts to be configured

[iainsproat]

Description & motivation

Postgres client configuration parameters were hard coded and could not be configured. This PR allows them to be configured by the server operator.

Changes:

• new environment variables to server, fileimport service, preview service, and webhook service to configure POSTGRES_CONNECTION_CREATE_TIMEOUT_MILLIS and POSTGRES_CONNECTION_ACQUIRE_TIMEOUT_MILLIS
• updates helm chart to provide db.connectionAcquisitionTimeoutMillis and db.connectionCreationTimeoutMillis configuration parameters and configure environment variables
• Helm Chart updated to allow postgresMaxConnections to be configured for fileimport service, preview service, and webhook service. These were previously configurable via environment variable but not via the Helm Chart.
• tidies environment variable parsing in preview service to use process.env['key'] syntax over process.env.key syntax.

To-do before merge:

Screenshots:

Validation of changes:

Checklist:

• My pull request follows the guidelines in the Contributing guide?
• My pull request does not duplicate any other open Pull Requests for the same update/change?
• My commits are related to the pull request and do not amend unrelated code or documentation.
• My code follows a similar style to existing code.
• I have added appropriate tests.
• I have updated or added relevant documentation.

References

[github-actions]

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