Serializer/Deserializer for JWT

This is a simple serde implementation to take the raw string, decode it from base64 and allow deserialization and serialization. What this does not do is handle the signature creation or verification.

Reasons

• JWTs are used with very different claims and contexts.
• Its more secure to have the developer choose their crypto libraries and decide what fields in the header and claims are relevant to them.
• This mostly deals with the common headaches involving base64 decoding and parsing the initial input string.