feat(metadata): authenticate /meta endpoints

[GeorgeMac]

Fixes FLI-119

This moves the following endpoints behind the gRPC authentication middleware:

• /meta/config
• /meta/info

This ensures when authentication is required that this information is not leaked.

To achieve this, the core implementation of these endpoints has been moved into a gRPC service of its own.
Such that it can be easily integrated in with the gRPC authentication middleware that exists.

This is done using gRPC gateways support for *runtime.HttpBody.

[codecov-commenter]

Codecov Report

Merging #1250 (22dc7fb) into main (d00b9aa) will not change coverage.
The diff coverage is n/a.

❗ Current head 22dc7fb differs from pull request most recent head 86d4320. Consider uploading reports for the commit 86d4320 to get more accurate results

@@           Coverage Diff           @@
##             main    #1250   +/-   ##
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  Coverage   80.22%   80.22%           
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  Files          41       41           
  Lines        3150     3150           
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  Hits         2527     2527           
  Misses        501      501           
  Partials      122      122           

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[markphelps]

nice