Support Route Entry Metadata in External Authorization Filter

[RiverPhillips]

Title: Support Route Entry Metadata in External Authorization Filter

Description:
External Authorization currently supports passing Dynamic Metadata. I would like to be able to pass metadata statically per route. This enhancement was made to the Rate Limiting filter in #13269 and I foresee the changes required by the External Authorization filter to be broadly similar.

After the changes it should be possible to configure it as follows:

metadata:
  filter_metadata:
    envoy.filters.external_authorization:
      foo: bar

This should result in foo being set on the filterMetadata map passed to ext_authz Check method

[RiverPhillips]

I would like to pick this up assuming it is an appropriate extension

[RyanTheOptimist]

cc: @esmet

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or "no stalebot" or other activity occurs. Thank you for your contributions.

[github-actions]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted" or "no stalebot". Thank you for your contributions.