Allow bulk adding of claims

[roberterdin]

Can you introduce a method in the JwtBuilder that allows for bulk insertation of claims but does not overwrite previously set ones?

Jwts.builder()
     .setClaims(someClaims) 
    .setSubject(someSubject)
    .signWith(SignatureAlgorithm.HS256, key)
    .compact();
// --> all good

Jwts.builder()
    .setSubject(someSubject)
    .setClaims(someClaims) 
    .signWith(SignatureAlgorithm.HS256, key)
    .compact();
// --> subject gets overwritten :(

While it is easy to avoid the overwriting it just makes the code prone to errors when the order of the builder functions matters.

Proposed solution.
Change the JwtBuilder and the Claims interfaces and implementations such that they allow an addClaims functions like this one in the DefaultJwtBuilder implementation.

    @Override
    public JwtBuilder addClaims(Map<String, Object> claims) {
        this.claims.putAll(claims)
        return this;
    }

I'm happy to submit a PR.

Cheers

[lhazlewood]

Thanks for the issue! A PR would be appreciated! Please add an @since 0.8.0 JavaDoc tag to the method before submission.

[petergphillips]

I've just been caught out by the setClaims method too, but for a different reason. The setClaims method takes a Map and then modifies the passed in map by adding the other claims to the map. This means that a immutable map (e.g. ImmutableMap or Collections.unmodifiableMap) can't be used in the builder. Modification of input parameters by an API is also not pleasant.

Would it be worth therefore deprecating the setClaims method altogether and moving to addClaims instead?

[lhazlewood]

PR merged - thank you!