breaking change: modify API for working with response metadata (#213)

* implement functions to append/get metadata and set/get status code

* сhanged behavior to return nil instead of empty metadata for getResponseMetadata()

* сhanged work with HTTP headers to use direct array assignment instead of for-range

* fix linters

* fix meter handler

* fix uninitialized response metadata for incoming context

* removed a useless test

* metrics handler has been fixed to work with compressed data

go.mod

@@ -1,8 +1,9 @@
 module go.unistack.org/micro-server-http/v4
 
-go 1.23.0
+go 1.24.0
 
 require (
+	github.com/stretchr/testify v1.10.0
 	go.unistack.org/micro-client-http/v4 v4.1.0
 	go.unistack.org/micro-codec-yaml/v4 v4.1.0
 	go.unistack.org/micro-proto/v4 v4.1.0
@@ -12,10 +13,12 @@ require (
 
 require (
 	github.com/ash3in/uuidv8 v1.2.0 // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
 	github.com/google/gnostic v0.7.0 // indirect
 	github.com/google/gnostic-models v0.6.9 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/matoous/go-nanoid v1.5.1 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/spf13/cast v1.7.1 // indirect
 	golang.org/x/sys v0.32.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20250428153025-10db94c68c34 // indirect