Support for Custom CA with RSA Keys

[randmonkey]

Problem Statement

From FTI-6433.

Customers attempting to use their own Certificate Authority (CA) with RSA (non-EC) keys to install the Kong Gateway Operator encounter failures. This issue is due to the operator's current limitation, which enforces Elliptic Curve (EC) cryptography for custom certificates. As a result, customers cannot proceed with installation if their CA uses RSA keys, even when the certificates are otherwise valid and secure.

Proposed Solution

• Develop a patch or feature update to include RSA support.
• Provide clear documentation and guidelines for customers on supported cryptographic algorithms.

Additional Information

Acceptance Criteria

• Users can use custom CAs with RSA keys
  • feat: add -cluster-ca-key-type and -cluster-ca-key-size flags to control the type and size (for rsa) of CA private keys #1081
• Have document to tell what algorithms of certificates are supported
  • kgo: add guide for customizing cluster CA docs.konghq.com#8386