This commit goes a long way toward making automated documentation of
Caddy config and Caddy modules possible. It's a broad, sweeping change,
but mostly internal. It allows us to automatically generate docs for all
Caddy modules (including future third-party ones) and make them viewable
on a web page; it also doubles as godoc comments.
As such, this commit makes significant progress in migrating the docs
from our temporary wiki page toward our new website which is still under
construction.
With this change, all host modules will use ctx.LoadModule() and pass in
both the struct pointer and the field name as a string. This allows the
reflect package to read the struct tag from that field so that it can
get the necessary information like the module namespace and the inline
key.
This has the nice side-effect of unifying the code and documentation. It
also simplifies module loading, and handles several variations on field
types for raw module fields (i.e. variations on json.RawMessage, such as
arrays and maps).
I also renamed ModuleInfo.Name -> ModuleInfo.ID, to make it clear that
the ID is the "full name" which includes both the module namespace and
the name. This clarity is helpful when describing module hierarchy.
As of this change, Caddy modules are no longer an experimental design.
I think the architecture is good enough to go forward.
This migrates a feature that was previously reserved for enterprise
users, according to https://github.com/caddyserver/caddy/issues/2786.
TLS session ticket keys are sensitive, so they should be rotated on a
regular basis. Only Caddy does this by default. However, a cluster of
servers that rotate keys without synchronization will lose the benefits
of having sessions in the first place if the client is routed to a
different backend. This module coordinates STEK rotation in a fleet so
the same keys are used, and rotated, across the whole cluster. No other
server does this, but Twitter wrote about how they hacked together a
solution a few years ago:
https://blog.twitter.com/engineering/en_us/a/2013/forward-secrecy-at-twitter.html
