feat: Do not print the secret key

[flub]

It is scary when folks have to worry about secrets being printed. #84
will solve the key persistence in a much better way anyway.

[flub]

I don't get the lint failure. My local rustfmt insists it is like this, the one on CI insists that. But both are stable rust?

[dignifiedquire]

this needs to be an option, if you want to reuse the key it needs to be printed so you can set it using the env variable

[matrss]

this needs to be an option, if you want to reuse the key it needs to be printed so you can set it using the env variable

I think it would be better to have a separate dumbpipe command to generate and print the secret, which can then be reused for subsequent dumbpipe commands.

In git-annex-p2p-iroh (https://git-annex.branchable.com/special_remotes/p2p/git-annex-p2p-iroh) the secret is generated with gpg because there is no easily parsable way to get it out of dumbpipe yet.