chore: pass frontend Sentry DSN

[latin-panda]

Follow-up from this work: getodk/web-forms#803 (PR#1610)

What has been done to verify that this works as intended?

Unit tests are passing. Docker is built with the correct client-config.json

Why is this the best possible solution? Were any other approaches considered?

It follows the same pattern as other variables are passed.

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Does this change require updates to documentation? If so, please file an issue here and include the link below.

Documented in the README file.

Before submitting this PR, please make sure you have:

• branched off and targeted the next branch OR only changed documentation/infrastructure (master is stable and used in production)
• verified that any code or assets from external sources are properly credited in comments or that everything is internally sourced

[lognaturel]

Want to make sure you’ve see #1998 in case it intersects!

[lognaturel]

We can put the second line in docs instead of here!

I haven’t looked deeply at how things are wired but wanted to flag that we’re working to switch to using a pre-built bundle in this release. So no problem if the var needs to be built into the image but it won’t be accessible for bundling.

[latin-panda]

As far as I understand, if #1998 lands, we won't be able to pass the DNS during build time, which is ideal, especially if we prefer not to track self-hosted instances.
@alxndrsn do you have a suggestion?

[latin-panda]

Is #1998 planned for this release?

[lognaturel]

#1998 is currently planned for this release because it addresses the significant increase in build memory needed after the Web Forms merger.

I think what would make the most sense for now is to include the DSN in /client-config.json to match the OIDC config.

[lognaturel]

Reopened a related Slack conversation!

[latin-panda]

@alxndrsn Could you please review when you have time?

PR to pass the DSN to the central-frontend
Issue for adding a proxy in the future

[alxndrsn]

Comments in-line.

[latin-panda]

@alxndrsn this is ready for another look! Thanks!