Integrate the failover client in ipfs-cluster-ctl

[hsanjuan]

Describe the feature you are proposing

ipfs-cluster-ctl should use the restapi LBClient with a Failover strategy.

Particularly, it should also be possible to create a Failover and a RoundRobin client strategy from a /dnsaddr. If the record resolves to multiple multiaddresses, each client should be initialized to one of them.

This needs a method to turn a single Config into multiple ones that can be used for NewLBClient, each of them with one multiaddress as resolved from the /dnsaddr. i.e. config.AsTemplateFor([]multiaddresses) []Config and config.AsTemplateForResolvedAddresses(multiaddress) []Config.

This should in the end enable ipfs-cluster-ctl to perform auto-failover to other resolved addresses in a multiaddress.

[omkarprabhu-98]

So the input through the command line would be a list of client config attributes that would be converted to a list of configs and then be passed to create the LBClient?

[hsanjuan]

The input form the command line would be ipfs-cluster-ctl --host /dnsaddr/my.host ....

Initializing the LB/Failover clients requires passing each 1 configuration for each endpoint in it. Thus, we need helper methods to, given a template configuration, produce multiple configs only changing the client multiaddress. As mentioned above, an additional method can actually perform resolving:

AsTemplateForResolvedAddresses(address) -> resolves -> calls AsTemplateFor(resolved_addresses).

Once you have these two helper methods, it should be easy to update ipfs-cluster-ctl to use the Failover client.