SOLR-17113: fix backup response in case of exception

[stforek]

Return exception as a json object instead of an array

https://issues.apache.org/jira/browse/SOLR-17113

Description

curl 'http://localhost:8983/solr/core/replication?command=details'

Returns exception as an array instead of an object:

{
    "responseHeader":{
      "status":0,
      "QTime":1
    },
    "status":"OK",
    "details":{
      //redacted
      "backup":["exception","The specified bucket does not exist."]
    }
  }

Solution

Replaced NamedList with SimpleOrderedMap which encodes as an object in json response.

Tests

Verified locally only. It looks that implementing a test case for this use case is difficult.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide

[cpoerschke]

Thanks for this contribution!

Would you like to add a solr/CHANGES.txt entry, in the 9.6.0 Bug Fixes section?

[gerlowskija]

LGTM - sorry for the delay in reviewing this, I've been offline for a few weeks!

re: merging - I don't want to step on your toes @cpoerschke , were you planning to test and merge, or should I? (Happy to do it, if needed)

[cpoerschke]

... re: merging - I don't want to step on your toes @cpoerschke , were you planning to test and merge, or should I? (Happy to do it, if needed)

Thanks for checking! Feel free to go ahead.