Add deploy/zyxel_gs1900.sh

[coderjoe]

Add support for deploying to the Zyxel GS1900 line of switches as long as those switches are running at least firmware V2.80.

Tested on a Zyxel GS1900-8 and GS1900-24E

Resolves #5042

[coderjoe]

I'm now using this version locally for my switches. Please let me know if there is anything you'd like me to do to improve the PR. No rush. :)

[coderjoe]

A bug has occurred on one of my servers with a different version of sed. Working on a fix now.

[coderjoe]

Most recent commit should have resolved the issue I found.

[coderjoe]

These are the differences between the two implementations and why I was using curl rather than _post. I have not been able to get _post to work.

[coderjoe]

I've updated for the shellcheck and shfmt linting in the previous run, have removed the defunct curl errors (now that curl is not a requirement) and have squashed the commit to clean up history a bit.

[coderjoe]

I've verified that the updated commits continue to work in all of my deployed environments.
Thank you very much @Neilpang for your help/guidance on wget support.

I don't think I would have figured it out without your suggestion. :)

[coderjoe]

I have now been using this in production for a few months. @Neilpang please let me know if there is anything else you would like me to do - or if there's anything I can do to help get this included. :)

Thanks again for your time and help!

[coderjoe]

Rebased onto the latest dev.
Please let me know what else needs to be done for a review.

[Neilpang]

why do you need to "ReadBodyFromFile"?

[coderjoe]

why do you need to "ReadBodyFromFile"?

Great question @Neilpang. I responded in the gitter.im chat while the repo was restricted, but I'll repeat it here just in case it wasn't seen.

I need to read from file because this switch expects a binary exact, not encoded, upload of the certificate. The uploaded certificate contains many \0 NULL bytes which cannot be piped within the shell script without being truncated.

Making wget or curl read the certificate file directly is the only way I have been able to get the full file uploaded in the manner the switch expects without the file becoming truncated by the null bytes.

I hope this helps clarify.