bug/Permit deleting db entries with leading slashes

[blast-hardcheese]

Why

A second attempt at #172, considering #172 (comment).

What changed

We added a DELETE method which supports multipart/form-data with fields key=${dbkey}. Canonical cURL example follows:

curl "$REPLIT_DB_URL" -X DELETE -F key=/my/slashy/key

Test plan

import asyncio
import os
import replit.database

def test():
    url = os.getenv('REPLIT_DB_URL')
    assert url
    db = replit.database.Database(url)

    print(list(db.keys()))
    print(db.set('/this/is/a/key', '/this/is/a/value'))
    print(list(db.keys()))
    # print(db.get('/this/is/a/key'))
    del db['/this/is/a/key']
    # print(db.get('/this/is/a/key'))
    print(list(db.keys()))

async def test_async():
    url = os.getenv('REPLIT_DB_URL')
    assert url
    db = replit.database.AsyncDatabase(url)

    print(await db.keys())
    print(await db.set('/this/is/a/key', '/this/is/a/value'))
    print(await db.keys())
    # print(await db.get('/this/is/a/key'))
    print(await db.delete('/this/is/a/key'))
    # print(await db.get('/this/is/a/key'))
    print(await db.keys())

test()
asyncio.run(test_async())

Rollout

Describe any procedures or requirements needed to roll this out safely (or check the box below)

• This is fully backward and forward compatible

[airportyh]

Are there plans to use multipart for other requests than delete?

[blast-hardcheese]

Loose plans, yes. We already support multipart for set, migrating that codepath as well could be beneficial.

We currently have a gap for get that could be benefitted by some out-of-band encoding, but POST for "get" semantics isn't great. Unfortunately the urlspace for get is already pretty crowded, which is why this PR is just to permit people to delete the keys they've set but can't otherwise read.