Currently servers exchange information about their WAN serf port
and RPC port with serf tags, so that they all learn of each other's
addressing information. We intend to make larger use of the new
public-facing gRPC port exposed on all of the servers, so this PR
addresses that by passing around the gRPC port via serf tags and
then ensuring the generated consul service in the catalog has
metadata about that new port as well for ease of non-serf-based lookup.
This refactor is to make it easier to see how serf feature flags are
encoded as serf tags, and where those feature flags are read.
- use constants for both the prefix and feature flag name. A constant
makes it much easier for an IDE to locate the read and write location.
- isolate the feature-flag encoding logic in the metadata package, so
that the feature flag prefix can be unexported. Only expose a function
for encoding the flags into tags. This logic is now next to the logic
which reads the tags.
- remove the duplicate `addEnterpriseSerfTags` functions. Both Client
and Server structs had the same implementation. And neither
implementation needed the method receiver.
And fix the 'value not used' issues.
Many of these are not bugs, but a few are tests not checking errors, and
one appears to be a missed error in non-test code.
R.B. Boyer