When using `mapstructure:",squash"`, most structure-specific hook don't
dive into the structure as they are provided with the parent structure.
Add an helper to make them work on the embedded structure as well and
use it for the generic "deprecated fields" hook, but also for the hook
for the common Kafka configuration.
This is a bit brittle. There are other use cases, but they may not need
this change.
Done with:
```
git grep -l 'for.*:= 0.*++' \
| xargs sed -i -E 's/for (.*) := 0; \1 < (.*); \1\+\+/for \1 := range \2/'
```
And a few manual fixes due to unused variables. There is something fishy
in BMP rib test. Add a comment about that. This is not equivalent (as
with range, random is evaluated once, while in the original loop, it is
evaluated at each iteration). I believe the intent was to behave like
with range.
revive default configuration has changed in 1.3.0. Some stuff is a bit
silly (like empty blocks), but I find it easier to follow that than to
try to tweak the configuration.
While there is more helpful information in a panic, this is confusing
to the user. With the amount of code using reflection, it seems better
to have clearer messages to help the user find the faulty section if
any.
This should be generalized to other parts of configuration (SNMP
community), however, we need to check what happens with default
values. Also, network definition in orchestrator is likely to be able
to reuse that.
This is a first step to accept another kind of GeoIP database (like
City). This also introduces the way we want to deprecate stuff:
transform the map structure.
