This module contains the database implementation for the KMS server. It provides functionality for interacting with different types of databases, such as SQLite, MySQL, PostgreSQL, and Redis.

The module includes the following submodules:

• cached_sqlcipher: Contains the implementation for caching SQL queries using SQLCipher.
• cached_sqlite_struct: Contains the implementation for caching SQLite structures.
• database_trait: Contains the trait definition for a generic database.
• mysql: Contains the implementation for MySQL database.
• object_with_metadata: Contains the implementation for objects with metadata.
• pgsql: Contains the implementation for PostgreSQL database.
• redis: Contains the implementation for Redis database.
• sqlite: Contains the implementation for SQLite database.
• locate_query: Contains utility functions for locating queries.
• migrate: Contains functions for database migration.
• retrieve_object_utils: Contains utility functions for retrieving objects.

The module also defines the following types and constants:

• KMSServer: A type alias for the KMS server.
• DBObject: A struct representing a database object.
• KMS_VERSION_BEFORE_MIGRATION_SUPPORT: A constant representing the KMS version before migration support.
• PGSQL_FILE_QUERIES: A constant representing the PostgreSQL file queries.
• MYSQL_FILE_QUERIES: A constant representing the MySQL file queries.
• SQLITE_FILE_QUERIES: A constant representing the SQLite file queries.

The module also includes the following functions:

• state_from_string: Converts a string to a StateEnumeration value.

Finally, the module includes a test module for unit testing.

Errors

This module does not define any specific errors. However, it may return errors from the underlying database operations or from the functions defined in the submodules. The specific error types and conditions are documented in the respective functions.