This commit reduces the interface to Load() a bit, in preparation for
unexporting NewBuilder and having everything call Load.
The three arguments are reduced to a single argument by moving the other
two into the options struct.
The three return values are reduced to two by moving the RuntimeConfig
and Warnings into a LoadResult struct.
And remove the devMode field from builder.
This change helps make the Builder state more explicit by moving inputs to the BuilderOps struct,
leaving only fields that can change during Builder.Build on the Builder struct.
Previsouly it was done in Agent.Start, which is much later then it needs to be.
The new 'dns' package was required, because otherwise there would be an
import cycle. In the future we should move more of the dns server into
the dns package.
This is a small step to allowing Agent to accept its dependencies
instead of creating them in New.
There were two fields in autoconfig.Config that were used exclusively
to load config. These were replaced with a single function, allowing us
to move LoadConfig back to the config package.
Also removed the WithX functions for building a Config. Since these were
simple assignment, it appeared we were not getting much value from them.
All commands which read config (agent, services, and validate) will now
print warnings when one of the config files is skipped because it did
not match an expected format.
Also ensures that config validate prints all warnings.
Previously the logic for reading ConfigFiles and produces Sources was split
between NewBuilder and Build. This commit moves all of the logic into NewBuilder
so that Build() can operate entirely on Sources.
This change is in preparation for logging warnings when files have an
unsupported extension.
It also reduces the scope of BuilderOpts, and gets us very close to removing
Builder.options.
