- cleaned up unused dependencies
- adds missing dependencies that are used in the code
- this should help us be more explicit about the dependencies a package
uses
refs https://github.com/TryGhost/Toolbox/issues/363
- this commit switches us to using the official and maintained
`mailgun.js` SDK, and updates the `mailgun-client` code to reflect the
changes between the two
- because of how the npm scripts were set up, we were running the full
Admin integration tests during the unit tests phase of CI
- this commit renames the majority of `test` to `test:unit` in the
package.json files, and aliases `test` to `test:unit`
- special packages like Admin have no-op'd `test:unit` scripts so we
don't end up running its tests
refs https://github.com/TryGhost/Toolbox/issues/363
- this commit pulls all code involving the Mailgun client SDK into one
new package called `mailgun-client`
- this means we should be able to replace `mailgun-js` (deprecated) with
`mailgun.js` (the new, official one) without editing code all over the
place
- this also lays some groundwork for better testing of smaller
components
