Add new option to install azure-cli extensions

[pauldotyu]

@jkeech and @asaikali - I have the code working which would resolve #149 but my solution for obtaining the remoteUser is a bit of a hack (for now). Will keep this as a draft PR until devcontainers/spec#91 is sorted out.

[pauldotyu]

With devcontainers/spec/issues/91 closed and env variable for user tested on vscode-remote-release/issues/7404, code has been updated to use the new env variable _REMOTE_USER when installing extensions.

This relies on Dev Containers extension v0.261.0 or higher and this will be ready merge once the latest extension goes into general release.

[pauldotyu]

@jkeech, would you be able to review this and let me know if I am missing anything?

[joshspicer]

Have you taken a stab at writing a scenario test for this change? I think it would be really useful.

We have some documentation on the concept here, as well as plenty of examples in this repo (one such example)

[joshspicer]

@pauldotyu - Also I am excited to share that with the newest build to the devcontainer CLI, we are injecting variables into Feature install.sh scripts with the effective remoteUser

We have some docs here - I think it will be really useful for what you're trying to accomplish with the su statement: https://containers.dev/implementors/features/#user-env-var

[pauldotyu]

Have you taken a stab at writing a scenario test for this change? I think it would be really useful.

We have some documentation on the concept here, as well as plenty of examples in this repo (one such example)

Thanks for pointing me to this. I've just added test scenario for some specific azure cli extensions

[pauldotyu]

@pauldotyu - Also I am excited to share that with the newest build to the devcontainer CLI, we are injecting variables into Feature install.sh scripts with the effective remoteUser

We have some docs here - I think it will be really useful for what you're trying to accomplish with the su statement: https://containers.dev/implementors/features/#user-env-var

Yes, I noticed the change was made to include the _REMOTE_USER environment variable and I am using that in my install script 😊

This PR should be ready for another review. Just let me know if I am missing anything else. Thanks!

[joshspicer]

Apologies for the delay, the Codespaces side of the team has been a busy few weeks leading up to GitHub Universe :)

Thanks for the contribution - this looks great :)