Add server certificates and private keys for various test cases

[t4niwa]

Description

In Go 1.25.2, the verification of X.509 certificate SANs (Subject Alternative Names) has been made stricter.

Certificates like the following are now treated as invalid:

• Domain names with a trailing dot (.): Such as the Fully Qualified Domain Name (FQDN) format example.com.
• Domain names with empty labels: Such as .example.com or example..com
• Labels exceeding 63 characters: Long domain names that exceed DNS label limits
• Improperly formatted email addresses: rfc822Name formats that do not comply with RFC 5322

A unit test was added to maintain backward compatibility.

Type of change

• Bug fix
• New feature
• Refactoring (no functional changes, no api changes)
• Non-code changes (update documentation, pipeline, etc.)

Flags

• Breaks backward compatibility
• Requires a documentation update
• Has untestable code

Related issue/PR

Delete this section if there are no issues or pull requests that relate to this pull request.

• Fixes #issue
• Closes #PR

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Checklist

• Followed the guidelines in the CONTRIBUTING document
• Added prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip] in the PR title if necessary
• Tested and linted the code
• Commented the code
• Made corresponding changes to the documentation
• Passed all pipeline checking

Checklist for maintainer

• Use Squash and merge
• Double-confirm the merge message has prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip]
• Delete the branch after merge

[Copilot]

Pull Request Overview

This PR adds test coverage for certificates with malformed Subject Alternative Names (SANs) to ensure backward compatibility with Go 1.25.2's stricter X.509 certificate validation. The Go version is updated from 1.25.1 to 1.25.3.

Key Changes:

• Updated Go version from 1.25.1 to 1.25.3
• Added test certificates and private keys with various SAN formatting issues
• Added test cases to verify these certificates load successfully

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
go.mod	Updated Go version to 1.25.3
test/data/trailing_dot_server.key	Private key for certificate with trailing dot in SAN
test/data/trailing_dot_server.crt	Certificate with trailing dot in SAN (e.g., example.com.)
test/data/malformed_email_server.key	Private key for certificate with malformed email in SAN
test/data/malformed_email_server.crt	Certificate with improperly formatted email address in SAN
test/data/long_label_server.key	Private key for certificate with DNS label exceeding 63 characters
test/data/long_label_server.crt	Certificate with DNS label exceeding 63 characters
test/data/leading_dot_server.key	Private key for certificate with leading dot in SAN
test/data/leading_dot_server.crt	Certificate with leading dot in SAN (e.g., .example.com)
test/data/empty_label_server.key	Private key for certificate with empty label in SAN
test/data/empty_label_server.crt	Certificate with empty label in SAN (e.g., example..com)
service/tls_test.go	Added test cases for malformed SAN certificates and fixed error handling logic

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