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🐛 Bug Report

When specifying a capitalized header in the schema of a request, the key shows up twice in the generated docs. Once with the capitalization, and once lowercased.

To Reproduce

Steps to reproduce the behavior:

Paste your code here:

// JsonSchema for my post request
 {
  headers: {
    type: 'object',
    required: ['Authorization'],
    properties: {
      // Fastify lowercases all headers https://github.com/fastify/help/issues/71
      Authorization: { type: 'string' }
    }
  }
 // ...etc
}

Expected behavior

The header should only show up once. With the capitalization that is specified.

Paste the results here:

Your Environment

• node version: v10.14.2
• fastify version: >= 2.4.1
• os: MacOS 10.14.6