Support opening a new channel during a settlement period

[pirapira]

When one channel is in the settlement period, the same pair of users should be able to create a new channel. Currently, a new channel can be created only after the first channel is settled.

[pirapira]

For this, we need to remove

• participants_hash_to_channel_identifier and
• getChannelIdentifier()

I have to check whether getChannelIdentifier() is being used.

[pirapira]

Not much, users usually remember the channel ID.

[pirapira]

I'll focus on #1087 now.

[pirapira]

I had a chat with @rakanalh about this.

The TokenNetwork proxy sometimes call getChannelIdentifier(). I'll try replacing the calls with errors, and see that ever happens.

[pirapira]

Somehow the client's smoketest calls getChannelIdentifier() raiden-network/raiden#4406.

[pirapira]

I looked through the client code. I think it's easy to remove all calls on getChannelIdentifier().

[pirapira]

Ah, but we need to change

 GET /api/(version)/channels/(token_address)/(partner_address)

to include a channel_id.

[pirapira]

Also
https://raiden-network.readthedocs.io/en/stable/rest_api.html#post--api-(version)-payments-(token_address)-(target_address)

POST /api/(version)/payments/(token_address)/(target_address)

would need to contain a channel_identifier here. Are people willing to add a channel_id here?

Perhaps we can change getChannelIdentifier() into getOpenChannelIdentifier().

[pirapira]

I'm finding relevant requirements: raiden-network/raiden#1769

As there should never exist more than 1 channel open for each tuple
(registry_address, token_address, own_address, partner_address)

So it's better to keep open channels unique.