Apply string casing to method params while deriving proxies and services

[Eligioo]

When providing RPC method parameters as a client via named parameters {"a": 1, "b": 2}, they had to be snake_cased since no string case renaming was applied to them inside the deriving macros. This PR changes this behaviour such that it adheres to the rename_all attribute that can be provided to the Proxy and Service macros.

Old input with service/proxy(rename_all = "camelCase") applied:

{
	"jsonrpc": "2.0",
	"method": "getElectionBlockAfter",
	"params": {
		"block_number": 33
	},
	"id": 1
}	

New input with service/proxy(rename_all = "camelCase") applied:

{
	"jsonrpc": "2.0",
	"method": "getElectionBlockAfter",
	"params": {
		"blockNumber": 33
	},
	"id": 1
}	

[sisou]

No idea how this magic works, so I'll have to try it out, which is a bit more work to do. Next week probably.

[blouflashdb]

Is this a breaking change for people that still use old casing?

[Eligioo]

Is this a breaking change for people that still use old casing?

@blouflashdb I would consider this a local breaking change yes and not protocol breaking one. If a client uses snake casing, it has to be updated. However I'm assuming that most users are using positional parameters thus not affect many.

[blouflashdb]

Please make it backwards compatible. Deprecate the old casing and remove it completely in a major version and add it to the breaking changes section in the upgrade notes.

I believe the next version will be a patch version? You can not expect from users to change their rpc usage in a patch version...

[Eligioo]

jsonrpc eventually ends up as a dependency used by the nimiq-client which follows its own SemVer. It's nowhere stated that this change is going to be included in the next release of the nimiq-client.

[hrxi]

Would probably be good to have a transition period where we accept both to be backward compatible.

[sisou]

This jsonrpc crate is published itself to crates.io. So it has it's own semver and @blouflashdb is right that this is a breaking change if the old style is not accepted anymore, requiring a new major version of this crate.

[jsdanielh]

LGTM