bugfix: convert metainfo from http style to rpc style (#16)

In previous codes, metainfo does not have a uniform style, and it
cannot work properly between different types of service.

We agree to use following rules:

- For RPC, use uppercase letters and `_` as separators when
  transmitting
- For HTTP, use lowercase letters and `-` as separators when
  transmitting
- For both protocols, use RPC style (uppercase with `_`) for storing
  keys of metainfo.

To implement this more elegantly, we defined a trait `Converter` and
use it for converting the key names between transmitting format and
storing format.

Signed-off-by: Yu Li <[email protected]>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "metainfo"
-version = "0.7.10"
+version = "0.7.11"
 authors = ["Volo Team <[email protected]>"]
 edition = "2021"
 description = "Transmissing metainfo across components."

src/backward.rs

@@ -15,13 +15,13 @@ pub trait Backward {
     fn set_backward_transient<K: Into<FastStr>, V: Into<FastStr>>(&mut self, key: K, value: V);
     fn set_backward_downstream<K: Into<FastStr>, V: Into<FastStr>>(&mut self, key: K, value: V);
 
-    fn strip_rpc_prefix_and_set_backward_downstream<K: Into<FastStr>, V: Into<FastStr>>(
+    fn strip_rpc_prefix_and_set_backward_downstream<K: AsRef<str>, V: Into<FastStr>>(
         &mut self,
         key: K,
         value: V,
     );
 
-    fn strip_http_prefix_and_set_backward_downstream<K: Into<FastStr>, V: Into<FastStr>>(
+    fn strip_http_prefix_and_set_backward_downstream<K: AsRef<str>, V: Into<FastStr>>(
         &mut self,
         key: K,
         value: V,