…configurations (open-component-model#864)

#### What this PR does / why we need it
- Added a new Go module in `bindings/go/rsa/signing/v1alpha1` to support RSA signing configurations.
- Implemented configurations for both `RSASSA-PSS` (probabilistic) and `RSASSA-PKCS1 v1.5` (deterministic) signature schemes.
- Introduced support for signature encoding policies (`Plain` and `PEM`) to manage signature serialization and storage.
- Added logic for media types, algorithms, and integration with runtime schemas.
- Autogenerated necessary deepcopy and runtime type management code for reusability.

#### Which issue(s) this PR fixes
- Lays groundwork for integrating modern cryptographic signing methods.
- Ensures backward compatibility with legacy PKCS1 v1.5 while promoting secure PSS usage.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

…for RSA signing handlers (open-component-model#865)

#### What this PR does / why we need it
- Consolidated `PSSConfig` and `PKCS1V15Config` into a single `Config` abstraction to simplify configuration handling for RSA signing.
- Added a new dynamic `Scheme` for consistent runtime type registration.
- Developed an extensive RSA handler test suite:
  - Covers both `RSASSA-PSS` and `RSASSA-PKCS1 v1.5` signature algorithms.
  - Includes tests for various signature encoding policies (`Plain` and `PEM`).
  - Added error path tests for unsupported algorithms, missing credentials, and tampered signatures.
- Enhanced identity handling for signing and verification configurations.

#### Which issue(s) this PR fixes
- Streamlines the configuration structure for RSA signing handlers.
- Ensures better test coverage and resilience for edge cases and error scenarios.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

…er and matcher

#### What this PR does / why we need it
- Replaced the internal `dn` package with a new `rfc2253` package to handle Distinguished Names (DNs) in compliance with RFC 2253.
  - Improved parsing of escaped characters, quoted values, and encoded forms like `#hex`.
  - Added robust test coverage for conformance, equality, and matching rules.
- Updated RSA signing handler to use the new `rfc2253` package for issuer verification.
- Eliminated old `dn` parsing and matching logic, simplifying the handling code.
- Enhanced error messages for DN matching failures for better clarity.
- Introduced options for lenient or strict DN parsing modes.

#### Which issue(s) this PR fixes

- Aligns DN parsing and matching with RFC 2253 specifications.
- Simplifies codebase by removing redundant and inconsistent logic.
- Improves resilience and correctness in X.509 issuer verification so we are actually using a proper parsing specification instead of a best effort parser like with ocm v1

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

…mental

#### What this commit does
- Changed the default signature encoding policy to `Plain` (`SignatureEncodingPolicyDefault`).
- Marked `PEM` signature encoding as experimental with warnings during signing and verification.
- Adjusted `handler.go` to use `context.Context` for logging warnings and improved code maintainability.

#### Why this is needed
- Aligns with simpler and more widely usable default (`Plain`) while leaving `PEM` as an experimental feature for selective use.
- Improves clarity for developers by explicitly marking experimental features and providing logging to reduce confusion.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

#### What this commit does
- Updated `Equal` function in `rfc2253` package to return errors instead of a boolean.
  - Allows better debugging and tracing of mismatches in Distinguished Names (DNs).
- Modified `handler.go` to handle errors returned by `Equal` and propagate detailed mismatch information.

#### Why this is needed
- Enhances error reporting for DN comparison issues, improving debugging and user feedback.
- Aligns with the goal of providing robust and clear validation mechanisms for X.509 issuer verification logic.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

…arity

#### What this commit does
- Simplifies the `ParseRSAPublicKeyPEM` function to return a single parsed `RSAPublicKeyPEM` when possible.
- Updates documentation to better describe supported PEM containers (`PKCS#1` and `PKIX`) and return behavior.
- Ensures function exits early if no PEM blocks are found, optimizing for clarity and correctness.

#### Why this is needed
- Reduces ambiguity in function usage by clarifying its behavior and supported formats.
- Aligns with clean code principles by improving readability and maintainability.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>

- Updated `ParseRSAPublicKeyPEM` documentation to include support for X.509 certificates.
- Improves clarity on accepted PEM container formats (`PKCS#1`, `PKIX`, and `X.509`).
- Enhances developer understanding of the function's capabilities and use cases.

Signed-off-by: Jakob Möller <jakob.moeller@sap.com>