Initialise OpenTelemetry

[whi-tw]

What problem does this pull request solve?

Trello card:

Similarly to govuk-forms/forms-runner#1841:

This will auto-hook into Rails and other libraries to produce traces.

No explicit trace spans are created yet, only automatic instrumentation.

The only explicit configuration is to avoid tracing the /up endpoint
used for health checks. This prevents a large number of unhelpful traces
from being created. All other configuration is provided through
environment variables, specified in forms-deploy.

We also disable logging for Rake tasks to avoid cluttering output
when running tasks like database migrations.

Finally, OpenTelemetry is only enabled if the ENABLE_OTEL environment
variable is set to "true". This allows us to control whether tracing
is active without changing the code. Again, this is configured in
forms-deploy when deploying to different environments.

Things to consider when reviewing

• Ensure that you consider the wider context.
• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🎉 A review copy of this PR has been deployed! You can reach it at: https://pr-2497.admin.review.forms.service.gov.uk/

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after 5 minutes, there may be something wrong with the ECS task. You will need to go to the integration AWS account
to debug, or otherwise ask an infrastructure person.

For the sign in details and more information, see the review apps wiki page.

[DavidBiddle]

Configuration looks sensible and consistent with what's been implemented in forms-runner 🎉