Integrate Sentry SDK for error reporting / tracking

[spwoodcock]

• We have a bunch of broken links etc on the website.
• As mentioned by David on slack, we could easily track using sentry-sdk
• We have an NGO account with Sentry and track errors in other tools with it.

Probably add to wsgi.py:

import sentry_sdk
sentry_sdk.init(
    dsn="https://examplePublicKey@o0.ingest.sentry.io/0",
    # Add data like request headers and IP for users;
    # see https://docs.sentry.io/platforms/python/data-management/data-collected/ for more info
    send_default_pii=True,
)

after getting a DSN from the Sentry dashboard.