sync up with API PR changes

[rgarcia]

the main / public Kernel API updates merged yesterday had some feedback on these endpoints--this syncs those changes in

I also filled out the implementation of process exec and added / refactored tests

https://github.com/onkernel/kernel/pull/416

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TL;DR

Syncs API endpoints with recent public API updates and implements the process.exec endpoint, including support for running commands as a specific user.

Why we made these changes

To incorporate feedback and align with recent updates to the main public Kernel API.

What changed?

• Updated openapi.yaml and the auto-generated oapi.go to match the latest public API contract.
• Implemented the process.exec endpoint, adding logic to buildCmd to handle execution as root (AsRoot) or a specific user (AsUser).
• Removed unsupported streaming-related code and comments from the ProcessExec endpoint.
• Added new tests to verify the AsRoot and AsUser functionality and refactored existing tests using stretchr/testify.

^{Description generated by Mesa. Update settings}

[mesa-dot-dev]

Performed full review of 5b79420...253b999

^{4 files reviewed | 1 comments | Review on Mesa | Edit Reviewer Settings}

[mesa-dot-dev]

This logic silently ignores non-numeric group specifiers. If a user passes something like "1000:wheel", the "wheel" group name will be silently ignored rather than being looked up or causing an error. Consider either:

1. Adding group name lookup similar to user lookup, or
2. Returning an error for non-numeric gid overrides to make the behavior explicit

Suggested change

	}
	if gidStr != "" {
	if gOverride, err := strconv.ParseUint(gidStr, 10, 32); err == nil {
	gid64 = gOverride
	} else {
	return nil, fmt.Errorf("gid override must be numeric, got %q", gidStr)
	}
	}

^{Type: Logic | Severity: Medium}

[Sayan-]

💯