Initial QSfera import

Server/services/groups/README.md

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+# Groups
+
+The `groups` service provides the CS3 Groups API for КуСфера. It is responsible for managing group information and memberships within the КуСфера instance.
+
+This service implements the CS3 identity group provider interface, allowing other services to query and manage groups. It works as a backend provider for the `graph` service when using the CS3 backend mode.
+
+## Backend Integration
+
+The groups service can work with different storage backends:
+- LDAP integration through the graph service
+- Direct CS3 API implementation
+
+When using the `graph` service with the CS3 backend (`GRAPH_IDENTITY_BACKEND=cs3`), the graph service queries group information through this service.
+
+## API
+
+The service provides CS3 gRPC APIs for:
+- Listing groups
+- Getting group information
+- Finding groups by name or ID
+- Managing group memberships
+
+## Usage
+
+The groups service is only used internally by other КуСфера services and not being accessed directly by clients. The `frontend` and `ocs` services translate HTTP API requests into CS3 API calls to this service.
+
+## Scalability
+
+Since the groups service queries backend systems (like LDAP through the configured identity backend), it can be scaled horizontally without additional configuration when using stateless backends.