unable to use ssh-ed25519 key: failed to create account: failed to create account: Internal

[alexcb]

Earthly only supports ssh-rsa (and ssh-rsa2 256/512) keys. Support is needed for ssh-ed25519.

[alexcb]

Currently the server returns a 500 error, which results in:

retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
retrying http request due to unexpected status code 500: Internal Server
Error
Error: failed to create account: failed to create account: Internal
Server Error

At the very least, the server should return:

1. some sort of permanent error, which would prevent the earthly client from re-attempting, and
2. a meaningful error message

[alexcb]

in order to support this, we will have to make changes to both the server and client; as we currently assume it's ssh-rsa in the client code, e.g. here: 561331d#diff-a59bcc9da3758e095acce0cf0e47eed93c85022529e353fb48d42f05ce2f418bR285

We should make this change before VERSION 0.7 is released.

[alexcb]

This is supported as of https://github.com/earthly/earthly/releases/tag/v0.6.27