Install intermediate SSL certificate on maven.k-int.com

Overview:

Gradle cannot download from https://maven.k-int.com because intermediate certificate is missing.

Steps to Reproduce:

1. Open build.gradle in mod-agreements or mod-licenses
2. Change http://maven.k-int.com/ to https://maven.k-int.com
3. Build

Expected Results:

The download from maven.k-int.com and the build succeed.

Actual Results:

The build fails because the download from maven.k-int.com fails with this error:

> Could not resolve com.k_int.grails:web-toolkit-ce:5.0.0.
         > Could not get resource 'https://maven.k-int.com/content/repositories/releases/com/k_int/grails/web-toolkit-ce/5.0.0/web-toolkit-ce-5.0.0.pom'.
            > Could not GET 'https://maven.k-int.com/content/repositories/releases/com/k_int/grails/web-toolkit-ce/5.0.0/web-toolkit-ce-5.0.0.pom'.
               > PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target 

Additional Information:

SSLLabs report: "This server's certificate chain is incomplete. Grade capped to B."
https://www.ssllabs.com/ssltest/analyze.html?d=maven.k-int.com

How to install a certificate:
https://www.ssl.com/faqs/faq-how-do-i-install-a-certificate/

Install Intermediate Certificates To Avoid SSL/TLS Not Trusted:
https://www.ssl.com/how-to/install-intermediate-certificates-avoid-ssl-tls-not-trusted/