File Upload, Part 1: Database modifications, Create file

[JamieTsai1024]

Notion ticket link

Implement File Upload

Implementation description

• Added new table for pdf files storage
• Added foreign key in intakes table for the pdf file
• Pass pdf file from form to backend to store in database
• Note: delete, update, and download file are handled in separate PRs

Steps to test

1. Add a new case

2. Fill out intake form and add an order referral file
   

3. Make sure that the pdf shows up in the pdf_file table once the form is submitted

What should reviewers focus on?

• Backend upload
• Database table creation

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR