Fix CF CLI GPG key installation for modern apt

[rileyseaburg]

Summary

Fix the GPG key installation for CloudFoundry CLI to work with modern apt.

Problem

The previous fix saved the ASCII-armored GPG key directly as a .gpg file, but modern apt requires the key to be in binary format.

Error was:

The key(s) in the keyring /etc/apt/trusted.gpg.d/cloudfoundry-cli.gpg are ignored as the file has an unsupported filetype.

Fix

• Use gpg --dearmor to convert the key to binary format
• Store in /usr/share/keyrings/ (preferred location for modern apt)

[Copilot]

Pull request overview

This PR fixes the CloudFoundry CLI GPG key installation to be compatible with modern apt by converting the ASCII-armored GPG key to binary format using gpg --dearmor and storing it in the recommended /usr/share/keyrings/ directory.

• Converts GPG key from ASCII-armored to binary format using gpg --dearmor
• Updates key storage location from /etc/apt/trusted.gpg.d/ to /usr/share/keyrings/
• Updates the signed-by path in the apt sources list configuration

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[Copilot]

The directory /usr/share/keyrings/ may not exist in all environments. The previous code created /etc/apt/trusted.gpg.d with mkdir -p before writing the key file. Consider adding a directory creation step before the gpg command to ensure reliability across different base images. For example: sudo mkdir -p /usr/share/keyrings before the wget/gpg command.

Suggested change

	# Download and convert the GPG key to binary format for modern apt
	# Download and convert the GPG key to binary format for modern apt
	sudo mkdir -p /usr/share/keyrings

[Copilot]

The directory /usr/share/keyrings/ may not exist in all environments. The previous code created /etc/apt/trusted.gpg.d with mkdir -p before writing the key file. Consider adding a directory creation step before the gpg command to ensure reliability across different base images. For example: sudo mkdir -p /usr/share/keyrings before the wget/gpg command.

Suggested change

	# Download and convert the GPG key to binary format for modern apt
	# Download and convert the GPG key to binary format for modern apt
	sudo mkdir -p /usr/share/keyrings