fix: Fix boot device selection crash

[adeatcu-ionos]

What does this fix or implement?

Fix boot device selection crash by providing a value for the error sentinel. With the previous version, the err was nil and this condition:

if err != nil {
		if errors.Is(err, cloudapiserver.ErrServerNotFound) {
			d.SetId("")
			return nil
		}
		return diag.FromErr(err)
}

Was not met, even when the server didn't exist.

Other observations:

• I provided a value for ErrSuspendCubeLast also, but this is rather used as a signal instead of an actual error, maybe this is not the right approach for this but redesigning it it's out of the scope of this PR

Checklist

• PR name added as appropriate (e.g. feat:/fix:/doc:/test:/refactor:)
• Tests added or updated
• Documentation updated
• Changelog updated and version incremented (label: upcoming release)
• Github Issue linked if any
• Jira task updated

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull Request Overview

This PR fixes a crash in the boot device selection functionality by properly initializing error sentinel values. The issue occurred because ErrServerNotFound was nil, preventing proper error handling when a server didn't exist.

Key Changes:

• Initialized ErrServerNotFound and ErrSuspendCubeLast sentinel errors with actual error values
• Updated changelog to document the fix

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
services/cloudapi/cloudapiserver/server.go	Initialized sentinel error variables with errors.New() to fix nil error checking
CHANGELOG.md	Added entry documenting the crash fix in version 6.7.18

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