Framework-free building blocks: null-safe helpers, error codes and pagination models

Database-portable persistence foundation: IDs, base entity, naming rules and query helpers

Append-only audit trail of security events

Tenants, user accounts, password hashing and first-run setup

The resource catalog (applications, menus, pages, buttons, APIs), roles and grants

Loads service type plugins: built-in ones from the classpath, external ones from the plugins directory, each in its own class loader

The OAuth 2.1 and OpenID Connect authorization server for applications of the catalog: their clients, the authorizations and tokens it issues, kept as hashes, and its rotating signing keys

The services of a tenant that plugins manage permissions of, such as an HDFS cluster: their configuration, with secrets encrypted, connection tests and resource lookups

Spring Boot application that serves the REST API and the web console