We are very inconsistent about how we're defining and using providers in the XML configuration. We need to meet the following requirements:

• Provide a single top-level element from the substitution group abstract-providers that specifies the providers to use in the absence of any other configuration; default to use-system-providers
• Update the following types (or appropriate enclosing type) to accept an optional nested abstract-providers override:
  • key-store-type
  • credential-store-type
  • hashed-password-type
• Update the following types to use an optional provider attribute (not nested element) to allow selection of a specific provider:
  • credential-store-type
  • key-store-type – already done!
  • hashed-password-type