SaaS Catalog: Add Custom Service

While LeanIX's SaaS catalog includes several thousand entries, there are cases where businesses are using non-supported SaaS vendors.

By enabling support for custom services, we intend to provide customers with the ability to manage their entire SaaS portfolio in LeanIX SMP.

Note: Custom services do not have any automated ingestion of spend and usage data. This data will be entered by customers either manually through UI or by scripts leveraging LeanIX's open API.