Add client config param IgnoreTURNResolveErrors

[amanakin]

Description

In some configurations we don't use the TURN address at the client side (e.g. proxy connection, see #450). But now at the client setup the provided turn address must be resolvable.

Adding client config param IgnoreTURNResolveErrors that allows omit resolving errors when we don't need turn address.

Also discussed here: pion/ice#773

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.57%. Comparing base (51f0d62) to head (752326c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #455      +/-   ##
==========================================
+ Coverage   67.43%   67.57%   +0.13%     
==========================================
  Files          43       43              
  Lines        3083     3087       +4     
==========================================
+ Hits         2079     2086       +7     
+ Misses        843      841       -2     
+ Partials      161      160       -1     

Flag	Coverage Δ
go	67.57% <100.00%> (+0.13%)	⬆️
wasm	26.36% <0.00%> (-0.04%)	⬇️

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[JoeTurki]

I don't think we should add a config, there are many reason, but it feels like a single use flag.
What if we make a new constructor NewClientWithResolver and essentially make the nested condition after if len(config.TURNServerAddr) > 0 { customizable, we can then make the current NewClient call this new constructor with the old resolver logic.

[JoeTurki]

Even better, we can use Pion options, pattern, and make NewClientWithOptions and make a custom option WithResolver.

[JoeTurki]

I can make a PR for this!

[amanakin]

@JoeTurki So you mean something like

if len(config.TURNServerAddr) > 0 {
	turnServ, err = config.ResolveTURN(config.TURNServerAddr)
	if err != nil {
		return nil, err
	}
}

And then in some cases use there WithResolveTURN(...) that will return nil, nil?

[amanakin]

@JoeTurki Any updates on this?