* Daemon: support remote configuration
This:
* Adds support for fetching the configuration from a remote HTTP location:
`ipfs-cluster-service init http://localhost:8080/ipfs/Qm...` will instruct
cluster to read the configuration file from ipfs on start (potentially making
use of ipns and dnslink).
This is done by creating a `service.json` like `{ "source": <url> }`.
The source is then read when loading that configuration every time the daemon starts.
This allows to let users always use a mutating remote configuration, potentially
adding/removing trusted peers from the list or adjusting other things.
* Configuration and state helpers from ipfs-cluster-service have been extracted
to its own cmdutils package. This will help supporting something like an
`ipfs-cluster-follow` command in the next releases.
* Allows to disable the rest api by not defining it in the configuration (I thought
this was already so, but apparently only affected the ipfsproxy).
* Removes informer/allocator configurations from the daemon (--alloc). No one used
a non default pair. In fact, it was potentially buggy to use the reposize one.
* Fix error messages (they must be in the form "doing something")
* Improve/reword some error messages
* Document the identity.json existance in the cli docs
* Fix a bunch of typos
* Fix missing folder path in the --help
* Fix cluster not locking when configuration is not there but folder is
* Fix force flag not overriding the config overwrite prompt
* Fix deletion of Raft state on re-init (not necessary if identity persists)
* Fix overwriting on identity (should not be overwritten if already exists)
Much of this paves the way to be able to run without service.json:
* Either taking default values (and using env vars) - maybe someday
* Either by getting a configuration template it from somewhere (ipfs, http)
at runtime - sooner.
