API Call 'missing HTTP content-type' error

[Nana-EC]

Description

In some local testing environments some devs are receiving missing HTTP content-type error from Block Node endpoints

ERROR:
  Code: Unknown
  Message: malformed header: missing HTTP content-type

Steps to Reproduce

1. Stand up a local instance of the Block Node
2. grpcurl the getBlock endpoint - grpcurl -plaintext -import-path <insertDir> -proto block_access_service.proto -d '{"retrieve_latest":"true"}' 127.0.0.1:8080 org.hiero.block.api.BlockAccessService.getBlock

Additional context

So far the issue has been observed in locla node and Solo.
We should confirm

1. If a local instance just with docker or JVM instance outside of those products experiences it
2. If in the case of a getBlock call the retrieve_latest being set to true is related. When set to false, it does not occur

[jsync-swirlds]

This is almost certainly an issue in the Helidon plugin, as we don't set, nor have access to set, HTTP headers from the block node code.

Very likely it relates at least partially to error handling in the plugin, based on the observed conditions.