Set mode when creating key file

[flokli]

Make sure a generated key file is not readable by others.

This ensures the file is not group/world-readable.

Before:

❯ ls -la /var/lib/mycelium/key.bin
-rw-r--r-- 1 root root 32 Feb 27 20:18 /var/lib/mycelium/key.bin

After:

❯ ls -la /var/lib/mycelium/key.bin
-rw------- 1 root root 32 Feb 27 20:34 /var/lib/mycelium/key.bin

[flokli]

I don't know why clippy on windows keeps failing, but seems unrelated:

Error: Unable to create clippy annotations! Reason: HttpError: Resource not accessible by integration

[LeeSmet]

The (current) clippy CI action has a limitation that it doesn't have the ability to put up anotations for PR's from forked repo's. The Issue is that the import for tokio::fs::OpenOptions isn't used on windows.

Could you change the code to either use a fully qualified path for OpenOptions, or add the import for it inside the unix { .. } block?

[flokli]

Done, and CI is now green!