Support inferring Path types from structs

[Flowneee]

PR #27 added path schema inferring from function arguments, but it doesn't implement inferring when T in Path<T> is complex struct. This should be fairly easy to implement if T implements JsonSchema - just extract its schema and check inner fields. So basically logic would be like:

1. get JSON schema for T;
2. if it is primitive type (string, number, ...) - assume this is single path parameter
3. if it is struct - assume each field is a separate parameter
4. if it is a tuple - probably the same

When T is struct, deserializer will use field names rather than positions, so crate should also validate that names of parameters in path matches field names in struct (probably via T JSON schema as well).

For tuples probably good idea to add number of positional arguments validation against actual path as well.