Implement --ephemeral flag

[ogenev]

When testing internal p2p network calls, we would like to be able to run multiple node instances simultaneously.
To avoid db folder collusion, we want to set unique db folder name for every node id.

As a default db folder, current implementation is using last 8 characters of base64 encoded Enr appended to the application name:
https://github.com/carver/trin/blob/d99232fd43c8dd0ec055150f382546cbba747bef/trin-core/src/utils.rs#L58

It will be better, if we change this to append the first few characters (instead of last 8) of the as-displayed node-id to the application name.

[pipermerriam]

When I was doing this in the python implementation I came up with the --ephemeral flag which took care of establishing a temporary directory in which all data would be housed. In most cases the desired shutdown behavior would be to cleanup this directory (delete it and all of its contents), though it would almost definitely be valuable to be able to retain this information. I would recommend potentially combining these two approaches ad doing this:

• Implement --ephemeral mode that uses a temporary directory within XDG_CACHE_HOME, using the node-id prefix solution outlined here for determining the directory
• Leave some sort of marker in that directory to signal when the directory was last used
• Maybe make some form of automation that will cleanup this directory, or alternatively, make the --ephemeral flag automatically purge the oldest directories once there are too many.

[mrferris]

It will be better, if we change this to append the first few characters (instead of last 8)

What's the reasoning for using the first few instead of last 8?

Now that I ask I'm guessing it's because the beginning part is more easily comparable by eye, like with git commit hashes.

[ogenev]

What's the reasoning for using the first few instead of last 8?

Now that I ask I'm guessing it's because the beginning part is more easily comparable by eye, like with git commit hashes.

Yeah, it is related to Jason's comment here.

[hmrtn]

PR #277 is ready for review 👍