Add IPv6 ClientConfig flag

[hetelek]

Adds a IPv6 flag to the turn.ClientConfig, which will allow for IPv6 relay support.

pion/ice#462

[Sean-Der]

@jech

[codecov]

Codecov Report

Merging #265 (801873f) into master (a4f7706) will increase coverage by 0.07%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #265      +/-   ##
==========================================
+ Coverage   68.05%   68.12%   +0.07%     
==========================================
  Files          38       38              
  Lines        2432     2438       +6     
==========================================
+ Hits         1655     1661       +6     
+ Misses        643      642       -1     
- Partials      134      135       +1     

Flag	Coverage Δ
go	68.12% <66.66%> (+0.07%)	⬆️
wasm	45.91% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
client.go	71.42% <66.66%> (+0.44%)	⬆️

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[jech]

@hetelek could you please explain why this is needed? Why is it not enough to infer the address family from ClientConfig.Conn, using something like:

network := config.Conn.LocalAddr().Network()

This would avoid adding a new API, and would give us more flexibility in the future if we decide that this is not the right approach.

If an explicit field is needed, I'd prefer it to be called Network and to be either a string or an int rather than a simple boolean, in case more values are needed in the future.

[stv0g]

This PR gets obsoleted if #276 gets merged.

[stv0g]

#276 has been merged. I therefore close this PR.