Enhance storage-cli webdav config

[kathap]

Needs new storage-cli release with cloudfoundry/storage-cli#70 to be in first

• A short explanation of the proposed change:
  Add support for optional signing_method configuration field in WebDAV/DAV storage-cli config templates across all Cloud Controller jobs. This allows operators to specify which URL
  signing method (SHA256 or MD5) the storage-cli should use when generating signed blobstore URLs.

• An explanation of the use cases your change solves

  1. BBL/CAPI Environments with MD5 Blobstore: Operators can now set signing_method: md5 in their manifest's connection_config blocks to generate URLs compatible with CAPI's existing
     nginx blobstore configuration, which only supports MD5 signed URLs.
  2. Flexible Migration Path: Enables gradual migration from MD5 to SHA256 signing methods by allowing different components to use different signing methods during transition periods.
  3. Environment-Specific Configuration: Allows the same CAPI release to work with both BOSH-style (SHA256) and CAPI-style (MD5) blobstores by simply configuring the signing method in
     the deployment manifest.
  4. Backward Compatibility: When signing_method is not specified, storage-cli defaults to SHA256 (BOSH-compatible), maintaining compatibility with existing BOSH-integrated
     deployments.

  Changes Made:

  • 20 config template files updated across 5 Cloud Controller job types:
    • cloud_controller_ng
    • cloud_controller_worker
    • cloud_controller_clock
    • cc_deployment_updater
    • blobstore_benchmark
  • 3 key modifications to each WebDAV/DAV config section:
    a. Added signing_method field pass-through (optional)
    b. Fixed endpoint to use private_endpoint + "/admin/" (correct authenticated upload path)
    c. Fixed TLS cert structure to {"cert":{"ca":ca_cert}} (correct storage-cli format)

  Example Manifest Usage:

   cc:
     buildpacks:
       blobstore_type: storage-cli
       blobstore_provider: webdav
       connection_config:
         username: blobstore-user
         password: ((password))
         private_endpoint: https://blobstore.internal:4443
         secret: ((blobstore_secret))
         signing_method: md5  # Optional: "md5" or "sha256", if not specified defaults to "sha256"

• Links to any other associated PRs

• I have viewed signed and have submitted the Contributor License Agreement

• I have made this pull request to the develop branch

• I have run CF Acceptance Tests on bosh lite