Enable configuration of "enable_trailers" protocol setting

pkg/api/getambassador.io/v3alpha1/crd_module.go

@@ -80,6 +80,9 @@ type Features struct {
 	// Should we enable http/1.0 protocol?
 	Http10 bool `json:"http10,omitempty"`
 
+	// Should we enable http response trailers?
+	Trailers bool `json:"trailers,omitempty"`
+
 	// Should we do IPv4 DNS lookups when contacting services? Defaults to true,
 	// but can be overridden in a [`Mapping`](/reference/mappings).
 	Ipv4Dns bool `json:"ipv4_dns,omitempty"`

python/ambassador/envoy/v3/v3listener.py

@@ -493,6 +493,10 @@ def base_http_config(self) -> Dict[str, Any]:
             http_options = base_http_config.setdefault("http_protocol_options", {})
             http_options["accept_http_10"] = self.config.ir.ambassador_module.enable_http10
 
+        if "enable_trailers" in self.config.ir.ambassador_module:
+            http_options = base_http_config.setdefault("http_protocol_options", {})
+            http_options["enable_trailers"] = self.config.ir.ambassador_module.enable_trailers
+
         if "allow_chunked_length" in self.config.ir.ambassador_module:
             if self.config.ir.ambassador_module.allow_chunked_length != None:
                 http_options = base_http_config.setdefault("http_protocol_options", {})

python/ambassador/ir/ir.py

@@ -1144,6 +1144,7 @@ def features(self) -> Dict[str, Any]:
             "use_remote_address",
             "x_forwarded_proto_redirect",
             "enable_http10",
+            "enable_trailers",
             "add_linkerd_headers",
             "use_ambassador_namespace_for_service_resolution",
             "proper_case",

python/ambassador/ir/irambassador.py

@@ -41,6 +41,7 @@ class IRAmbassador(IRResource):
         "default_labels",
         "diagnostics",
         "enable_http10",
+        "enable_trailers",
         "enable_ipv4",
         "enable_ipv6",
         "envoy_log_format",
@@ -141,6 +142,7 @@ def __init__(
             # comment in crd_module.go.
             use_proxy_proto=False,
             enable_http10=False,
+            enable_trailers=False,
             proper_case=False,
             prune_unreachable_routes=True,  # default True; can be updated in finalize()
             use_remote_address=use_remote_address,

python/tests/unit/test_listener_http_protocol_options.py

@@ -47,6 +47,14 @@ def test_proper_case_and_enable_http_10():
     )
 
 
+@pytest.mark.compilertest
+def test_proper_case_and_enable_http_10():
+    yaml = module_and_mapping_manifests(["proper_case: true", "enable_trailers: true"], [])
+    _test_listener_http_protocol_options(
+        yaml, expectations={"enable_trailers": True, "header_key_format": {"proper_case_words": {}}}
+    )
+
+
 @pytest.mark.compilertest
 def test_allow_chunked_length_false():
     yaml = module_and_mapping_manifests(["allow_chunked_length: false"], [])