Add missing media type

[charithag]

Purpose

Add missing media type definitions

Goals

Prevent Unsupported Media type error with JSON

Approach

Add json as consume and produce media types

User stories

N/A, bug fix

Release note

N/A, bug fix

Documentation

N/A, bug fix

Training

N/A, bug fix

Certification

N/A, bug fix

Marketing

N/A, bug fix

Automation tests

N/A, bug fix, already covered with produce integration tests

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? yes
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes

Samples

N/A, bug fix

Related PRs

N/A, bug fix

Migrations (if applicable)

N/A, bug fix

Test environment

Fedora 23, x64, Oracle JDK 1.8.91

Learning

N/A, bug fix