Fixes after review

Author: r4victor

contributing/BACKENDS.md

@@ -118,7 +118,7 @@ Refer to examples:
 
 Under the backend directory you've created, create the `compute.py` file and define the
 backend compute class that extends the `dstack._internal.core.backends.base.compute.Compute` class.
-It can also extend and implement `ComputeWith*` classes to support additional features such as fleets, volumes, gateways, placement groups, etc.
+It can also extend and implement `ComputeWith*` classes to support additional features such as fleets, volumes, gateways, placement groups, etc. For example, it should extend `ComputeWithCreateInstanceSupport` to support fleets.
 
 Refer to examples:
 [datacrunch](https://github.com/dstackai/dstack/blob/master/src/dstack/_internal/core/backends/datacrunch/compute.py),

src/dstack/_internal/server/services/backends/__init__.py

@@ -369,7 +369,7 @@ async def get_instance_offers(
     return sorted(offers, key=lambda i: not i[1].availability.is_available())
 
 
-def check_backed_type_available(backend_type: BackendType):
+def check_backend_type_available(backend_type: BackendType):
     if backend_type not in list_available_backend_types():
         raise BackendNotAvailable(
             f"Backend {backend_type.value} not available."

src/dstack/_internal/server/services/gateways/__init__.py

@@ -39,7 +39,7 @@
 from dstack._internal.server.db import get_db
 from dstack._internal.server.models import GatewayComputeModel, GatewayModel, ProjectModel
 from dstack._internal.server.services.backends import (
-    check_backed_type_available,
+    check_backend_type_available,
     get_project_backend_by_type_or_error,
     get_project_backend_with_model_by_type_or_error,
 )
@@ -538,7 +538,7 @@ def gateway_model_to_gateway(gateway_model: GatewayModel) -> Gateway:
 
 
 def _validate_gateway_configuration(configuration: GatewayConfiguration):
-    check_backed_type_available(configuration.backend)
+    check_backend_type_available(configuration.backend)
     if configuration.backend not in BACKENDS_WITH_GATEWAY_SUPPORT:
         raise ServerClientError(
             f"Gateways are not supported for {configuration.backend.value} backend."

src/dstack/_internal/server/services/volumes.py

@@ -376,7 +376,7 @@ async def generate_volume_name(session: AsyncSession, project: ProjectModel) ->
 def _validate_volume_configuration(configuration: VolumeConfiguration):
     if configuration.volume_id is None and configuration.size is None:
         raise ServerClientError("Volume must specify either volume_id or size")
-    backends_services.check_backed_type_available(configuration.backend)
+    backends_services.check_backend_type_available(configuration.backend)
     if configuration.backend not in BACKENDS_WITH_VOLUMES_SUPPORT:
         raise ServerClientError(
             f"Volumes are not supported for {configuration.backend.value} backend."