Update signing key environment variable

[devcrocod]

Change the property name to search for GPG_SECRET_KEY

Motivation and Context

enable signing publications

Breaking Changes

no

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[Copilot]

Pull Request Overview

Updates the Gradle publishing script to look for a different environment variable when loading the GPG signing key.

• Renames the expected environment/Gradle property key from GPG_SIGNING_KEY to GPG_SECRET_KEY.
• Alters the configuration contract for supplying the signing key.

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

Changing the expected key from GPG_SIGNING_KEY to GPG_SECRET_KEY drops support for the previously recognized environment/Gradle property name and may break existing build environments despite the PR stating there are no breaking changes. Consider supporting both (preferring the new one) to preserve backward compatibility, e.g.: val gpgKeyNames = listOf("GPG_SECRET_KEY", "GPG_SIGNING_KEY"); val signingKey = gpgKeyNames.map { providers.environmentVariable(it).orElse(providers.gradleProperty(it)) }.reduce { acc, p -> acc.orElse(p) }. Or document the intentional breaking change.

Suggested change

	val gpgKeyName = "GPG_SECRET_KEY"
	val gpgPassphraseName = "SIGNING_PASSPHRASE"
	val signingKey = providers.environmentVariable(gpgKeyName)
	.orElse(providers.gradleProperty(gpgKeyName))
	val gpgKeyNames = listOf("GPG_SECRET_KEY", "GPG_SIGNING_KEY")
	val gpgPassphraseName = "SIGNING_PASSPHRASE"
	val signingKey = gpgKeyNames
	.map { providers.environmentVariable(it).orElse(providers.gradleProperty(it)) }
	.reduce { acc, p -> acc.orElse(p) }