explicitly return a string for String method instead of panic

[acornett21]

• Relates: updating operator manifest tools with fixed panic and adding test case redhat-openshift-ecosystem/openshift-preflight#1390
• Methods that implement Stringer, should never panic. Returning <invalid> so it's clear to the caller that something is wrong.

[Copilot]

Pull request overview

This PR updates the pkg/imagename.ImageName String() implementation to avoid panicking when string formatting fails, aligning fmt.Stringer behavior with the expectation that String() should be safe for callers.

Changes:

• Replace panic(err) in (*ImageName).String() with a sentinel return value ("<invalid>") on error.
• Add an explanatory comment documenting why String() must not panic.

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[Copilot]

Pull request overview

This PR updates ImageName.String() (a fmt.Stringer implementation) to avoid panicking on invalid image names by returning "<invalid>", and adds test coverage for invalid ImageName values.

Changes:

• Change ImageName.String() to return "<invalid>" when formatting fails, instead of panicking.
• Add Ginkgo table tests asserting String() returns "<invalid>" for invalid ImageName struct states.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
pkg/imagename/imagename.go	Replaces panic-on-error behavior in String() with a sentinel string return.
pkg/imagename/imagename_test.go	Adds table-driven tests for invalid ImageName.String() behavior.

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[Copilot]

Pull request overview

This PR updates the ImageName String() implementation to avoid panicking (even for invalid or nil receivers) and adds tests ensuring invalid image names produce a stable, explicit placeholder string.

Changes:

• Updated (*ImageName).String() to return "<invalid>" instead of panicking on invalid state/errors.
• Added Ginkgo table-driven tests covering nil/invalid ImageName cases for String().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
pkg/imagename/imagename.go	Makes String() nil-safe and non-panicking by returning "<invalid>" on failure.
pkg/imagename/imagename_test.go	Adds coverage to ensure String() returns "<invalid>" for several invalid ImageName shapes.

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[Copilot]

Pull request overview

This PR updates the ImageName String() implementation to avoid panicking on invalid values (including a nil receiver) and instead return a clear sentinel string (<invalid>), aligning with Stringer expectations.

Changes:

• Add <invalid> sentinel constant for representing invalid ImageName stringification results.
• Update (*ImageName).String() to return <invalid> instead of panicking (and to handle nil receivers safely).
• Add table-driven tests covering invalid ImageName cases (including nil) to ensure String() does not panic.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pkg/imagename/imagename.go	Introduces <invalid> sentinel and makes String() return it on nil/invalid state instead of panicking.
pkg/imagename/imagename_test.go	Adds Ginkgo table tests verifying String() returns <invalid> for invalid/nil ImageName.

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