feat: add environment variables to canister settings

[rikonor]

See https://dfinity.atlassian.net/browse/SDK-2151.

This change is required to add support for canister environment variables in the
new icp-cli tool.

[lwshang]

The field name must be consistent with the spec:

type canister_settings = record {
    ...
    environment_variables : opt vec environment_variable;
}

So we should use environment_variables instead of environment.

For consistency, I also suggest these naming changes, though they don't affect correctness:

• Rename the key-value pair type : Variable -> EnvironmentVariable;
• Rename the builder methods: with_environment_variables, with_optional_environment_variables.

During my Rust CDK work, I found Pocket-IC doesn't support this feature yet, so we can't properly test it right now. The incorrect field name was actually skipped during Candid deserialization since it's an optional field, meaning our existing tests (including those in the PR) wouldn't catch this error.

[rikonor]

During my Rust CDK work, I found Pocket-IC doesn't support this feature yet, so we can't properly test it right now.

I spoke with @mraszyk yesterday about this, and he referred me to this PR which should bring support to pocket-ic. I will try to test with it shortly and report back.

[rikonor]

The field name must be...

Thanks for the feedback @lwshang, I'll make the changes and report back 👍

[mraszyk]

The PR is now merged: please use master commits/artifacts for PocketIC.

[lwshang]

For integration tests, we should test the updated CreateCanisterBuilder and UpdateCanisterBuilder with some env vars set. Then call canister_status to verify the env vars really take effect.

[rikonor]

For integration tests, we should test the updated CreateCanisterBuilder and UpdateCanisterBuilder with some env vars set. Then call canister_status to verify the env vars really take effect.

@lwshang - would you be able to provide some guidance on how to go about adding an integration test to this repo? This is the first time I've worked with this repo so I am not sure if there's some established approach.

[lwshang]

would you be able to provide some guidance on how to go about adding an integration test to this repo?

Sure. The ref-tests crate contains the integration tests of the repo. The ic-utils related tests are in this file.

For guidance on how to run the tests locally, you can refer to this CI workflow.