Delete TURN allocation on socket close

[sgfn]

Use ExTURN.Client.close/1 to send Refresh(lifetime=0) and delete the present allocation.

Resolves #100

ref: elixir-webrtc/ex_turn#10

[sgfn]

@joaothallis

Rationale behind my changes to your branch:

1. Don't trap exits: We don't expect ExWebRTC to crash, preparing for it seems a bit overkill. A fix for the crash on ExWebRTC.DTLSTransport.close/1 is coming
2. Don't call ExTURN.Client.close/1 on clients in gathering_transactions: these clients are not :allocated yet, they "move" to local_cands on :allocation_created. The additional cleanup step would only deal with the corner case where we received the :allocation_created message, but have yet to process it during teardown -- not worth covering IMHO
3. Logger.warning -> debug: There's virtually nothing the user can do when that final send fails, and we'd rather keep the verbosity level low

Comments are welcome:)

[Karolk99]

NITPICK
It looks nice (if ExTURN.close/1 returns {:ok, state} it automatically returns), but on the other hand it would be better to always return the same value.

Suggested change

	defp release_turn_allocation(ice_agent, socket, client) do
	with {:send, turn_addr, data, _client} <- ExTURN.Client.close(client) do
	case ice_agent.transport_module.send(socket, turn_addr, data) do
	:ok -> :ok
	{:error, reason} -> Logger.debug("Couldn't send deallocate request, reason: #{reason}")
	end
	end
	end
	defp release_turn_allocation(ice_agent, socket, client) do
	with {:send, turn_addr, data, _client} <- ExTURN.Client.close(client) do
	:ok <- ice_agent.transport_module.send(socket, turn_addr, data) do
	:ok
	else
	{:ok, _state} -> :ok
	{:error, reason} -> Logger.debug("Couldn't send deallocate request, reason: #{reason}")
	end
	end
	end

[Karolk99]

If that can cause problems for the user, maybe info would be better.

[sgfn]

I don't think there's anything the user can do in this case, as this most likely suggests a network issue. I'd leave it at debug

[Karolk99]

We should look more closely at whether we need to close TURN allocations in cases when handle_terminate won't be called (when PeerConnection is closed with a different reason than :normal)

[sgfn]

We should look more closely at whether we need to close TURN allocations in cases when handle_terminate won't be called (when PeerConnection is closed with a different reason than :normal)

Reverted back to trapping exits, now allocations are released during shutdowns and parent crashes, too

[codecov]

Codecov Report

❌ Patch coverage is 85.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.08%. Comparing base (f428324) to head (0491b26).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/ex_ice/ice_agent.ex	75.00%	1 Missing ⚠️
lib/ex_ice/priv/ice_agent.ex	83.33%	1 Missing ⚠️
test/support/transport/mock.ex	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #101      +/-   ##
==========================================
+ Coverage   86.86%   87.08%   +0.22%     
==========================================
  Files          27       27              
  Lines        2078     2091      +13     
==========================================
+ Hits         1805     1821      +16     
+ Misses        273      270       -3     

Files with missing lines	Coverage Δ
lib/ex_ice/ice_agent.ex	69.51% <75.00%> (+0.28%)	⬆️
lib/ex_ice/priv/ice_agent.ex	88.81% <83.33%> (+0.46%)	⬆️
test/support/transport/mock.ex	82.85% <90.00%> (+2.21%)	⬆️

... and 1 file with indirect coverage changes

---

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