Add ability to output the `presentation` value of a file entity by providing its `slug` in the request

[baddlan]

Sample use case: CSS link tag <link rel="stylesheet" href="{{cms}}{{environment}}/files/{{file-slug}}">

This will require knowing the mime type of the file.

[StephenOTT]

Looking at the sample payload from the CMS postman examples, mime type appears to be a missing field and a oversight. mime type should be added as a field when POST /files

[StephenOTT]

Related issue for adding Mime Type: #3

[StephenOTT]

@baddlan can you give a example of a file tag?

[baddlan]

Sorry, by file tag I meant slug. I'll update the title and description of the issue.

[marioprudhomme]

Done.