Flask 2.1.0 lacks an upper bound for werkzeug, and the latest version
is not compatible.

Uninett has merged with NSD and Unit to become Sikt.

Tag incidents with organization names rather than UUIDs

See merge request !1

Because incidents are for human consumption.

Use a TTLCache with a 24 hour timeout.

When a secret is configured, expect all requests to contain a
X-Mist-Signature-v2 header with a signature: HMAC-SHA256(secret, body) -
otherwise, reject the request as unauthenticated.

Helps us detect WHERE incorrect secrets are configured in Mist

This still lacks a few significant features:
- Customer ID mapping to name
- Does not protect against duplicates
- Lookup of incident-to-resolve may not be robust enough

Also include pyargus into requirements, so we can talk to an Argus API
server.

Also, document the settings.

Because:
- This is more suitable when running in a container, as planned.

Additionally, reformat the code.