Implement upload

[MantisClone]

Try to upload the file without storing to filesystem. Should stream it ideally.

When user calls upload assume that they've already approved our EOA to withdraw WETH from their account.

Required Workflow

1. Validate upload request
2. Validate quote ID, nonce, and signature
3. Double-check that quote is still valid by calling Bundlr.price(bytes)
4. Return 200
5. Set quote status to 2

• Pull WETH from user's account into our EOA using transferFrom(userAddress, amount) #41
• Unwrap WETH to ETH #42

8. Fund our EOA's Bundlr Account using Bundlr.fund()
9. Set quote status to 3
10. Set quote status to 4
11. Download the file(s) from the URI(s)
12. Upload the file(s) to Arweave using Bundlr.upload(file)

• HEAD request to Arweave Gateway to verify that file uploaded successfully #43

14. Set quote status to 5

Note
Update quote status in database throughout.

Note
Consider combining step 4 and 5. Stream downloaded file straight into Bundlr

Failure Modes

• Invalid Upload request
• Price to upload exceeds quote
• File length exceeds quote
• approval amount too low
• Node RPC not reachable
• File size exceeds Bundlr funds
• ...

Stretch Goal: Withdraw leftover funds after upload.
See for details: https://github.com/users/MantisClone/projects/1/views/1