Add allowedValues support for API parameter discovery

[dheeraj12347]

Summary

This PR adds support for exposing allowed parameter values through the API Discovery framework.

Framework changes

• Add allowedValues attribute to the @Parameter annotation
• Extend ApiParameterResponse to expose allowed values
• Update ApiDiscoveryServiceImpl to populate allowedValues

API annotations

Add allowedValues annotations to representative API parameters with fixed documented values.

The annotations cover:

• Snapshot APIs
• Backup Schedule APIs
• Firewall APIs
• IP Forwarding APIs
• Template APIs
• ISO APIs
• VPC Offering APIs

Testing

Successfully built using:

mvn -pl api,plugins/api/discovery -am -DskipTests clean install

I also investigated runtime verification using the simulator. The simulator Docker image runs from an embedded source tree, so local source changes require rebuilding the simulator image before they are reflected in listApis.

[DaanHoogland]

@blueorangutan package

[blueorangutan]

@DaanHoogland a [SL] Jenkins job has been kicked to build packages. It will be bundled with no SystemVM templates. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result [SF]: ✖️ el8 ✖️ el9 ✖️ debian ✖️ suse15. SL-JID 18464

[codecov]

Codecov Report

❌ Patch coverage is 30.76923% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 20.40%. Comparing base (a4a52c9) to head (0270119).
⚠️ Report is 105 commits behind head on main.

Files with missing lines	Patch %	Lines
.../cloudstack/api/response/ApiParameterResponse.java	0.00%	6 Missing ⚠️
.../cloudstack/discovery/ApiDiscoveryServiceImpl.java	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13543      +/-   ##
============================================
+ Coverage     18.08%   20.40%   +2.31%     
- Complexity    16721    18786    +2065     
============================================
  Files          6037     5757     -280     
  Lines        542580   520931   -21649     
  Branches      66428    60824    -5604     
============================================
+ Hits          98149   106293    +8144     
+ Misses       433409   403057   -30352     
- Partials      11022    11581     +559     

Flag	Coverage Δ
uitests	?
unittests	20.40% <30.76%> (+1.15%)	⬆️

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