fix(azkv): handle whitespace in Azure Key Vault URLs

[sEpt0r]

Problem:

The Azure Key Vault key parser would fail when URLs contained leading or trailing whitespace, which commonly occurs when using YAML Block Scalar syntax.

creation_rules:
  - azure_keyvault: >-
      https://test.vault.azure.net/keys/test-key/a2a690a4fcc04166b739da342a912c90,
      https://test2.vault.azure.net/keys/another-test-key/cf0021e8b743453bae758e7fbf71b60e

This resulted in the error:

could not parse " https://test2.vault.azure.net/keys/another-test-key/cf0021e8b743453bae758e7fbf71b60e" into a valid Azure Key Vault MasterKey

Fix:

• Added strings.TrimSpace() to clean the URL before parsing in NewMasterKeyFromURL()
• Added test case to verify handling of URLs with leading/trailing spaces