Reduce expiration time of certificates (#1146)

Clients that rely on OSX APIs for certificate validation may find an error
with the message "certificate is not standards compliant" with certificates
that don't comply with Apple rules for certificate validation. When this error
happens, the actual reason for each certificate is not exposed, and it
seems to happen with certificates that should be valid in the context of
the validation.
More discussion about this can be found in golang/go#51991.

This happens with certificates generated by `elastic-package`, clients
sometimes report this error with configurations that otherwise should accept
these certificates.

According to this post, one of the rules is that certificates cannot be valid for
more than 825 days.
https://rahulkj.github.io/openssl,/certificates/2022/09/09/self-signed-certificates.html

Reduce the expiration time to try to reduce the chances of triggering this error.

Author: jsoriano

internal/certs/certs.go

@@ -152,7 +152,9 @@ func New(isCA bool, issuer *Issuer, opts ...Option) (*Certificate, error) {
 		return nil, fmt.Errorf("failed to get a unique serial number: %w", err)
 	}
 
-	const longTime = 100 * 24 * 365 * time.Hour
+	// Don't use a expiration time longer than 825 days.
+	// See https://rahulkj.github.io/openssl,/certificates/2022/09/09/self-signed-certificates.html.
+	const longTime = 800 * 24 * time.Hour
 	template := x509.Certificate{
 		NotBefore: time.Now(),
 		NotAfter:  time.Now().Add(longTime),