docs: Add Operating Flynn page

[titanous]

First pass.

@jvatic Please implement redirects from the added JSON file in the server.

Closes #2074
Closes #1189
Closes #2659
Closes #2070
Closes #478
Refs #1286

[jvatic]

@titanous Can you add redirects_path to docs/lib/flynn-docs.rb?

[titanous]

@jvatic Done.

[jvatic]

LGTM

[lmars]

I have seen some users have /var/lib/flynn on a dedicated disk, so is it worth clarifying what "existing filesystem" means? For example:

By default, a ZFS pool is created in a sparse file on the
same filesystem that `/var/lib/flynn/volumes` exists on.

[titanous]

Comments addressed.

[philiplb]

We recommend running Flynn with low-TTL round-robin DNS A records pointing at
each host. For automatic failover, health checks should be configured that
automatically remove a host's A record if it is unhealthy.

What does that mean, how would I implement the A records? After adding them in the DNS server, where would I configure them within Flynn, if so?

[lmars]

@philiplb your DNS records are not managed from within Flynn, but by whatever service your domain's nameserver records point at.

You can use a service like AWS Route53 to manage your DNS records with health checks as proposed in the document.

[lmars]

LGTM

[philiplb]

Of course, this is what I meant with DNS server. Ok, this simply says to have a failover machine for each of the (initial) nodes.