:sparkles: Handle NotFound and UnprocessableEntity errors in middleware

[ff137]

Closes #3322

Currently, NotFound and UnprocessableEntity errors would print stack traces in the logs. It is more sensible to record these as info logs, since they typically represent bad requests / client errors.

This PR contributes changes so that the new behaviour will print messages like:

Not Found error occurred during GET /connections/abe80270-051c-415b-9bb1-b74a86846276: Record not found: connection/abe80270-051c-415b-9bb1-b74a86846276

Unprocessable Entity occurred during GET /connections: {'querystring': {'their_public_did': ['Value None is not a valid DID']}}

A util method extract_validation_error_message was added to help print this marshmallow validation error, so that the logs still provide the error context previously contained in the stack trace.

---

:art: Other minor amendments included as well:

• logger.warn is deprecated in favour of logger.warning, so replaced one instance
• there were 2 error logs ("Note: setting ledger to read-only mode"). I opted to set these to warning level
• refactored ready_middleware to reduce complexity
• modified a fatal log to critical instead of error level

[ff137]

5.0% Duplication on New Code (required ≤ 3%)

Can we increase this threshold to something more pragmatic? 10-20% would make sense

[jamshale]

5.0% Duplication on New Code (required ≤ 3%)

Can we increase this threshold to something more pragmatic? 10-20% would make sense

We can, but it's a bit of an annoying process because none of the maintainers have admin rights on the sonarcloud project right now. There is ways to set setting in the sonar-project.properties file and the github action but I haven't experimented much with this. For now I think we'll just have to comment when you think something should be ignored, but I would like to clean some of these reports up in the future.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
91.7% Coverage on New Code
0.7% Duplication on New Code

See analysis details on SonarCloud