Document missing tests and server features (#432)

Sources/SwiftGRPCNIOInteroperabilityTests/InteroperabilityTestCases.swift

@@ -17,6 +17,18 @@ import Foundation
 import SwiftGRPCNIO
 import NIOHTTP1
 
+/// Missing tests:
+/// - client_compressed_unary
+/// - server_compressed_unary
+/// - client_compressed_streaming
+/// - server_compressed_streaming
+/// - compute_engine_creds
+/// - jwt_token_creds
+/// - oauth2_auth_token
+/// - per_rpc_creds
+/// - google_default_credentials
+/// - compute_engine_channel_credentials
+
 /// This test verifies that implementations support zero-size messages. Ideally, client
 /// implementations would verify that the request and response were zero bytes serialized, but
 /// this is generally prohibitive to perform, so is not required.

Sources/SwiftGRPCNIOInteroperabilityTests/ServerFeatures.swift

@@ -26,6 +26,12 @@ import NIOHTTP1
 /// These features are listed in the [gRPC interoperability test description
 /// specification](https://github.com/grpc/grpc/blob/master/doc/interop-test-descriptions.md).
 ///
+/// Missing features:
+/// - compressed response
+/// - compressed request
+/// - observe `ResponseParameter.interval_us`
+/// - echo authenticated username
+/// - echo authenticated OAuth scope
 ///
 /// - Note: This is not a complete set of features, only those used in either the client or server.
 public enum ServerFeature {