fix(sql): Optimize getFreeSubscribersWaitingForMonthlyEmail

[jbuck]

References:

Jira: MNTOR-
Figma:

Description

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Not applicable.

How to test

Checklist (Definition of Done)

• Localization strings (if needed) have been added.
• Commits in this PR are minimal and have descriptive commit messages.
• I've added or updated the relevant sections in readme and/or code comments
• I've added a unit test to test for potential regressions of this bug.
• If this PR implements a feature flag or experimentation, I've checked that it still works with the flag both on, and with the flag off.
• If this PR implements a feature flag or experimentation, the Ship Behind Feature Flag status in Jira has been set
• Product Owner accepted the User Story (demo of functionality completed) or waived the privilege.
• All acceptance criteria are met.
• Jira ticket has been updated (if needed) to match changes made during the development process.
• Jira ticket has been updated (if needed) with suggestions for QA when this PR is deployed to stage.

[Vinnl]

@rhelmer Would you mind if I defer to you for this one? Since you wrote the original query (#5431), which I don't fully comprehend :) I'd primarily look out for en-US matching us, and nl-BE not matching nl, for example.

[rhelmer]

I'm not sure a paramaterized query is used in this case, and I don't know if we can guarantee that countryCodes has been sanitized.

[rhelmer]

To make sure it's parameterized I think something like this would work (untested):

.whereRaw(
  `fxa_profile_json ->> 'locale' ~ '^..-(' || ? || ')'`,
  [countryCodes.join("|")]
)