Implement redacting of fields for MPA, apply it to httpoverrpc

[sfc-gh-mwalas]

Currently httpoverrpc is unusable with MPA as every single request need to be separately approved. This change ignores requests to the server while constructing MPA.

[sfc-gh-elinardi]

could you also update

sansshell/services/mpa/README.md

Line 81 in 4777f2e

If you use OPA for authz, you'll also need to update the server's rego policies to reject requests that unexpectedly set `proxied-sansshell-identity` metadata if it allows callers other than the proxy to make direct calls. If you fail to do so, a direct caller can manipulate the metadata to approve their own request. For example, the policy below will reject calls if proxied identity information is in the metadata and the caller is something other than a peer with an identity of `"proxy"`.

and https://github.com/Snowflake-Labs/sansshell/pull/562/files#diff-2604a9e725510ddcf1204e208d3d7ec2894cdcd4274c856c1a45df50128c4085L107 please?

Another q: after this change, the MPA approval will be valid for any requests to the same {hostname, port, tlsconfig, and protocol} correct?

[sfc-gh-mwalas]

Sorry, I got this just for testing purposes in place, we shouldn't merge this change to default policy.

Re the second point, indeed the MPA for httpoverrpc will become valid after this change for all combination of {hostname, port, tlsconfig, and protocol}, after a debate on what are meaningful levels of authz policy for MPA here we ended up saying that for httpoverrpc current MPA of each request does not make much sense.

[sfc-gh-elinardi]

update copyright year