Trailer limits

[ioquatix]

There are only a few trailers that probably make sense to be merged into headers. So by default, only allow a small subset, like etag, digest, date, etc.

Technically this is a breaking change, as applications shouldn't depend on trailers, they can be dropped anyway.

However, in some cases, like grpc, we need to specifically reinterpret the headers. That is done by creating a custom policy that allows grpc-status as a trailer and applying it to the headers.

Types of Changes

• New feature.
• Breaking change.
• Security.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.