Add HMAC signature support for JWT

[ldclakmal]

Purpose

This PR adds the HMAC signature support for JWT according to the Section-3.2 of RFC 7518 [1].

The following "alg" (algorithm) Header Parameter values are used to
indicate that the JWS Signature is an HMAC value computed using the
corresponding algorithm:

             +-------------------+--------------------+
             | "alg" Param Value | MAC Algorithm      |
             +-------------------+--------------------+
             | HS256             | HMAC using SHA-256 |
             | HS384             | HMAC using SHA-384 |
             | HS512             | HMAC using SHA-512 |
             +-------------------+--------------------+

[1] https://datatracker.ietf.org/doc/html/rfc7518#section-3.2

Examples

Sample Issuer Config

jwt:IssuerConfig issuerConfig = {
    username: "John",
    issuer: "wso2",
    audience: ["ballerina", "ballerinaSamples"],
    expTime: 600,
    signatureConfig: {
        algorithm: jwt:HS256,
        config: "s3cr3t"
    }
};

Sample Validator Config

jwt:ValidatorConfig validatorConfig = {
    issuer: "wso2",
    audience: ["ballerina", "ballerinaSamples"],
    clockSkew: 60,
    signatureConfig: {
        secret: "s3cr3t"
    }
};

Fixes ballerina-platform/ballerina-library#1645

Checklist

• Linked to an issue
• Updated the changelog
• Added tests

[codecov]

Codecov Report

Merging #307 (85a307f) into master (ced3626) will decrease coverage by 2.27%.
The diff coverage is 52.17%.

❗ Current head 85a307f differs from pull request most recent head 5f53d42. Consider uploading reports for the commit 5f53d42 to get more accurate results

@@             Coverage Diff              @@
##             master     #307      +/-   ##
============================================
- Coverage     82.19%   79.92%   -2.28%     
  Complexity       31       31              
============================================
  Files            11       11              
  Lines           691      752      +61     
  Branches        330      369      +39     
============================================
+ Hits            568      601      +33     
- Misses          116      144      +28     
  Partials          7        7              

Impacted Files	Coverage Δ
ballerina/jwt_commons.bal	100.00% <ø> (ø)
ballerina/jwt_validator.bal	78.48% <44.73%> (-3.24%)	⬇️
ballerina/jwt_issuer.bal	81.45% <61.29%> (-4.12%)	⬇️

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