Make AuthInfo.expiresAt mandatory since it is validated as mandatory at runtime

[Nick-Lucas]

expiresAt is currently an optional key in AuthInfo, but requireBearerAuth runtime validates that is it set. This is misleading when implementing an authenticated MCP Server because MCP Clients will only see that they're not authenticated after authentication due to their token being assumed as expired immediately

typescript-sdk/src/server/auth/middleware/bearerAuth.ts

Lines 67 to 70 in c94ba4b

	if (typeof authInfo.expiresAt !== 'number' || isNaN(authInfo.expiresAt)) {
	throw new InvalidTokenError("Token has no expiration time");
	} else if (authInfo.expiresAt < Date.now() / 1000) {
	throw new InvalidTokenError("Token has expired");

Motivation and Context

Misleading types causing a broken auth flow

How Has This Been Tested?

Updated unit tests

Breaking Changes

The change to runtime validating this is set occured in a previous release, so this fixes the type accuracy

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• [ X] I have read the MCP Documentation
• [ X] My code follows the repository's style guidelines
• [ X] New and existing tests pass locally
• [ X] I have added appropriate error handling
• [ X] I have added or updated documentation as needed

Additional context