feat: extensibility ums destination changes

[hariturangi]

Description

UMS Destination - New connectivity model

This change is needed because the AppFND team suggested using an existing destination name (sap-managed-runtime-ias-${landscape}) instead of creating a new destination name (sap-managed-runtime-ums-${landscape}) to read the extensions.
Hence, the current code needs to be modified to use the one the AppFND team suggested.

Environment variable support:
Added APPFND_CONHOS_UMS_URL to enable the new IAS-based flow

Dynamic destination resolution:
When APPFND_CONHOS_UMS_URL is set → uses IAS destination (sap-managed-runtime-ias-{landscape})
Otherwise → falls back to legacy UMS destination (sap-managed-runtime-ums-{landscape})

URL resolution logic:
New flow: Base URL from APPFND_CONHOS_UMS_URL environment variable

Legacy flow: Base URL from destination configuration
Both flows: mTLS certificate always from the resolved destination

Related Issue

NA
(Link to the GitHub issue this PR addresses)

Type of Change

Please check the relevant option:

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Dependency update

How to Test

Describe how reviewers can test your changes:

1. Step 1
2. Step 2
3. Expected result

Checklist

Before submitting your PR, please review and check the following:

• I have read the Contributing Guidelines
• I have verified that my changes solve the issue
• I have added/updated automated tests to cover my changes
• All tests pass locally
• I have verified that my code follows the Code Guidelines
• I have updated documentation (if applicable)
• I have added type hints for all public APIs
• My code does not contain sensitive information (credentials, tokens, etc.)
• I have followed Conventional Commits for commit messages

Breaking Changes

There are no breaking changes. We have BCT (Backwards Compatibility) enabled; if the env variable is not found, then it will go with old behaviour

Additional Notes

Tested in the local agent and it worked.

[cla-assistant]

All committers have signed the CLA.

[NicoleMGomes]

I believe we can remove the ums destination since this was never provisioned on managed runtime

[NicoleMGomes]

Better to not keep the two ways so code is more readable

[hariturangi]

There are some existing agents that are referring to this destination, which are manually created

[NicoleMGomes]

Ok, but the new approach should work for all agents since it's automated, no need to keep this work-around on sdk. And if the new approach is not there, they don't need to adopt the new version right now.

[hariturangi]

Modified the code as suggested

[NicoleMGomes]

How have you validated these changes? On which agent?

[hariturangi]

How have you validated these changes? On which agent?

We have an agent https://github.tools.sap/agent-extensibility-test/extensibility-tools-agent; I have started this agent locally and applied the SDK changes to this agent