Добавлен общий код PerxisDataProvider, GrpcChannel и моделей

https://tracker.yandex.ru/AUTO-1373

review @teplyakov

perxis/channel.py

+from typing import Optional
+
+import grpc
+
+from perxis.auth import APIKeyPlugin
+from perxis.models import PerxisEnviron
+
+
+class GrpcChannel:
+    call_credentials: grpc.CallCredentials
+    channel_credentials: grpc.ChannelCredentials
+    composite_credentials: grpc.ChannelCredentials
+    channel: Optional[grpc.Channel] = None
+
+    def __init__(
+        self,
+        target: str,
+        metadata_plugin: grpc.AuthMetadataPlugin,
+        project_name: str,
+        project_version: str,
+        call_credentials_name: str = "api-key",
+    ) -> None:
+        self.target = target
+        self.metadata_plugin = metadata_plugin
+        self.call_credentials_name = call_credentials_name
+        self._init_credentials()
+        self.connect(project_name, project_version)
+
+    def _init_credentials(self) -> None:
+        self.call_credentials = grpc.metadata_call_credentials(
+            self.metadata_plugin, name=self.call_credentials_name
+        )
+        self.channel_credentials = grpc.ssl_channel_credentials()
+        self.composite_credentials = grpc.composite_channel_credentials(
+            self.channel_credentials, self.call_credentials
+        )
+
+    def connect(self, project_name: str, project_version: str) -> None:
+        if not self.channel:
+            self.channel = grpc.aio.secure_channel(
+                self.target, self.composite_credentials,
+                options=(
+                    ("grpc.primary_user_agent", f"{project_name}/{project_version}"),
+                )
+            )
+
+    async def close(self) -> None:
+        await self.channel.close()
+
+
+def get_grpc_channel(perxis_environ: PerxisEnviron, project_name: str, project_version: str) -> GrpcChannel:
+    return GrpcChannel(
+        target=perxis_environ.target,
+        metadata_plugin=APIKeyPlugin(token=perxis_environ.api_key),
+        project_name=project_name,
+        project_version=project_version
+    )