Allow sanitiseContentFor parameter in sendEmail method

[kr8n3r]

What problem does the pull request solve?

notify-api already accepts sanitize_content_for optional payload - an array of personalisation keys
that is sanitises.

This PR extends the Node client to accept the optional parameter sanitiseContentFor in the sendEmail method
Tests and type definitions also updated.

Input with sanitiseContentFor

personalisation: {
    name: 'click [evil link](https://evil.link)',
    link: 'Amala, please [click this evil link](https://evil.link)'
  },
sanitiseContentFor:['link']

Response

{
  content: {
    body: 'click [evil link](https://evil.link)\r\n' +
      '\r\n' +
      'this is the link Amala, please \\[click this evil link\\]\\(\\)',
  },
  sanitised_content: {
    link: {
      sanitised: 'Amala, please \\[click this evil link\\]\\(\\)',
      unsanitised: 'Amala, please [click this evil link](https://evil.link)'
    }
  },

Input without sanitiseContentFor

personalisation: {
    name: 'Amala',
    link: 'click [evil link](https://evil.link)'
  },

Response

{
  content: {
    body: 'Amala click [evil link](https://evil.link)\r\n'
  },
  sanitised_content: {},

Delivered message with and without sanitisation

Checklist

• I’ve used the pull request template
• I’ve written unit tests for these changes
• I’ve updated the documentation in
  • notifications-tech-docs repository
  • CHANGELOG.md
• I’ve bumped the version number in
  • package.json
• I've added new environment variables in
  • CONTRIBUTING.md
  • notifications-node-client/scripts/generate_docker_env.sh

[CrystalPea]

Well done on this! I left a couple comments - let me know what you think.