feat(adms): add SAP ADMS module with sync/async clients and BDD tests

[adwitiyasushant]

Summary

Adds a new sap_cloud_sdk.adms module providing a Python client for SAP's
Attachment Document Management Service (ADMS), along with the shared SDK
building blocks it depends on (IAS X.509 token fetcher, mTLS support, async
HTTP client, telemetry entry).

ADMS is the BTP service that lets agentic and business applications attach
documents to business object nodes (purchase orders, sales orders, etc.) with
virus scanning, scoped downloads, and audit metadata. This module is the
prerequisite for higher-level agent workflows that read/write documents on
behalf of users.

What's included

Public API (sap_cloud_sdk.adms)

• AdmsClient (sync) and AsyncAdmsClient with sub-namespaces:
  • client.documents.* — document CRUD, content download URLs, scan-state
    gating
  • client.relations.* — DocumentRelation lifecycle (create / get / list /
    update / delete) plus draft create-validate-activate-discard flow
  • client.config.* — ConfigurationService reads (allowed domains,
    document types, BO node types, type→BO mappings)
• create_client() / create_async_client() factories that load the IAS
  binding from a mounted secret volume with env-var fallback.

Auth / HTTP

• IasTokenFetcher (core.auth) — IAS client_credentials flow with the
  resource parameter that scopes the JWT's aud claim to the ADM
  application.
• AdmsHttp / async variant — typed get / get_list / post / patch /
  delete helpers with OData error → typed exception mapping
  (DocumentNotFoundError, ScanNotCleanError, ConfigError, etc.).
• mTLS helpers in core.auth._mtls.

Tests

• 187 unit tests covering models, HTTP layer, sub-namespace APIs, retry/error
  mapping, and config resolution.
• pytest-bdd integration tests with Gherkin scenarios
  (tests/adms/integration/document_flow.feature,
  async_flow.feature) — skipped when the service URL isn't configured.
• Adds Module.ADMS to the telemetry enum.

Why one squashed commit

This branch was rebased onto main and squashed before opening the PR to
remove unrelated UCL prototype commits and version drift. Full review-by-review
history is preserved on my fork at backup/contrib-adms-pre-rebase.

Verification

uv run ruff check src/sap_cloud_sdk/adms/   # ✓
uv run ty check --python-version 3.11 src/sap_cloud_sdk/adms/   # ✓
uv run python -m pytest tests/adms/unit/ -q   # ✓ 187 passed

Adds a full-featured ADMS (Attachment Document Management Service) module to the SDK with sync and async clients, IAS X.509 token authentication, OData V4 service support (DocumentService, ConfigurationService, AdminService), and pytest-bdd integration tests with Gherkin scenarios.

Also adds shared SDK building blocks consumed by ADMS: IAS token fetcher, mTLS support, async HTTP client, and the ADMS telemetry module entry.

> **Disclaimer:** Do not include SAP-internal or customer-specific information in this PR (e.g. internal system URLs, customer names, tenant IDs, or confidential configurations). This is a public repository.

## Description

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## Related Issue

Closes #<issue_number>

(Link to the GitHub issue this PR addresses)

## Type of Change

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- [ ] 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

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## Checklist

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- [ ] I have read the [Contributing Guidelines](../CONTRIBUTING.md)
- [ ] 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](../docs/GUIDELINES.md)
- [ ] 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.)
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## Breaking Changes

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