Programmatic tagging

Please help.

My department publishes a lot of pdf documents on a monthly basis, so I am trying to create a shiny app that allows different people to upload the document(s) to Rstudio and tag the document (I have already created the tag schema on Rstudio Connect).
I was thinking something where the person uploads the document, and provide some metadata (i.e. title, date, etc.) which are sufficient for the API to essentially do everything (publishing, tagging, etc.)

Any help or ideas on how I can go about building such an app?

Simplify the example in a dialog box and capture to csl-json for further use.