fleet/third_party/httpsig-go/testdata/key-rsa-v15.pub

Added a vendored version of httpsig-go. (#30820) For #30473 This change adds a vendored `httpsig-go` library to our repo. We cannot use the upstream library because it has not merged the change we need: https://github.com/remitly-oss/httpsig-go/pull/25 Thus, we need our own copy at this point. The instructions for keeping this library up to date (if needed) are in `UPDATE_INSTRUCTIONS`. None of the coderabbitai review comments are relevant to the code/features we are going to use for HTTP message signatures. We will use this library in subsequent PRs for the TPM-backed HTTP message signature feature. <!-- This is an auto-generated comment: release notes by coderabbit.ai --> ## Summary by CodeRabbit * New Features * Introduced a Go library for HTTP message signing and verification, supporting multiple cryptographic algorithms (RSA, ECDSA, Ed25519, HMAC). * Added utilities for key management, including JWK and PEM key handling. * Provided HTTP client and server helpers for automatic request signing and signature verification. * Implemented structured error handling and metadata extraction for signatures. * Documentation * Added comprehensive README, usage examples, and update instructions. * Included license and configuration files for third-party and testing tools. * Tests * Added extensive unit, integration, and fuzz tests covering signing, verification, and key handling. * Included official RFC test vectors and various test data files for robust validation. * Chores * Integrated continuous integration workflows and ignore files for code quality and security analysis. <!-- end of auto-generated comment: release notes by coderabbit.ai --> 2025-07-14 18:26:50 +00:00			`-----BEGIN PUBLIC KEY-----`
			`MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCvgZyuyxbY+pIzNWy+x7QkEKQl`
			`49ZmbQkwE8+B2UvUA+Xhoru0VnUlvnXdKaBpnzhNxktn6HwLd6CYqZlfLTVvbgeD`
			`WE8KuXxW9DJi9+AQ0AUKOqGwjgJMelBtIfMvdWPg6fZXCsDfvjvJkcOmx4lcnwEy`
			`Zt4YEh55oIisi9MiRQIDAQAB`
			`-----END PUBLIC KEY-----`