Add support for file uploads

[InsOpDe]

Addresses issues #782 #93
Took most code from #96 - so props to ezra-quemuel. sadly his code didnt got merged and it was too much of a hassle to merge his PR with the current code. This PR should fix this and add one of the most wanted features to tsoa

I decided not to store files send to the server, instead let the developer decide what to do with the received buffer.

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Test plan

Added 2 unit tests for each middleware (hapi, koa and express) one for testing whether the actual issue works, another one for testing multiple text-fields (plus multiple files) being uplaoded at once.

[WoH]

Can you add missing spec tests for OpenAPI 2/3?
One of the reason this currently is tedious is the manual spec writing.

[InsOpDe]

Will do

[InsOpDe]

• Removed file[] type as we have array
• Added negative test cases for checking that an error is thrown if the keynames are wrong in a multipart/form-data upload
• Added multiple methods which ensure that formData generates a valid requestBody for uploads. Also overwrote return value for dataType which changed from file to string with binary in openapi3
• Added openApi v2 and v3 tests which verify that a valid swagger file is generated (regarding to file upload)
• Run tests with https://editor.swagger.io/ to ensure that the GUI is properly rendered

[WoH]

LGTM, thanks a lot for submitting the PR

[joel1st]

Thanks for this work! Have been using TSOA for nearly 3 years and very excited to see this land.

Just some quick questions (I can put up a documentation PR after I've confirmed)

• Because files are loaded into memory, I guess this should only be used for small/non frequent uploads (eg a large video upload could crash the server from OOM / a lot of smaller assets being uploaded concurrently) https://www.npmjs.com/package/multer#user-content-memorystorage

• If we did want to get around this limitation is there a way to change the multer configuration? or should we use the old approach?

[WoH]

You can either use the old approach, adapt the route template, or submit a PR that allows you to hook into/provide the config we pass to multer.
Other approaches are probably less advisable.