Checkout  https://github.com/adobe/aem-core-wcm-components/blob/main/bundles/core/src/test/java/com/adobe/cq/wcm/core/components/internal/models/v1/contentfragment/ContentFragmentImplTest.java for Junit. 

Lightroom API: https://developer.adobe.com/lightroom/lightroom-api-docs/api/ 

The client ID and client secret combination are invalid.If this is not the case, contact the Adobe Support team to resolve it. 

Change the log level to trace and then replicate the issue to see detailed logs. 

Check https://blog.developer.adobe.com/adobe-document-cloud-sdk-and-aem-integration-feda412c680f to see if it helps in integration.

You can check https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/assets/admin/xmp-metadata.html?lang=en to see if you can avoid implementing com.day.cq.dam.api.handler.xmp.XMPWriteBackOption in your custom code.If this is not possible, contact Adobe Support Team.

Although PostgreSQL is not supported in AEM 6.5 and above, as mentioned in https://experienceleague.adobe.com/docs/experience-manager-65/deploying/deploying/rdbms-support-in-aem.html?lang=en.But you can still check with Adobe Support Team if this is true for AEM as Cloud. For a list of supported dat...

Refer: https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/implementing/developing/generating-access-tokens-for-server-side-apis.html?lang=en

Refer: https://experienceleaguecommunities.adobe.com/t5/adobe-livecycle-questions/cannot-set-a-checkbox-to-required-quot-user-entered-required/m-p/117067

https://experienceleague.adobe.com/docs/journey-optimizer/using/get-started/ajo-integrations.html?lang=en for integration.