server: implement data persistence with database

Using databases + sqlite/postgresql depending of what you want.
Use DATABASE_URL to configure

Closes #70

server/reflector/db/__init__.py

@@ -0,0 +1,42 @@
+import databases
+import sqlalchemy
+from reflector.events import subscribers_startup, subscribers_shutdown
+from reflector.settings import settings
+
+
+database = databases.Database(settings.DATABASE_URL)
+metadata = sqlalchemy.MetaData()
+
+
+transcripts = sqlalchemy.Table(
+    "transcript",
+    metadata,
+    sqlalchemy.Column("id", sqlalchemy.String, primary_key=True),
+    sqlalchemy.Column("name", sqlalchemy.String),
+    sqlalchemy.Column("status", sqlalchemy.String),
+    sqlalchemy.Column("locked", sqlalchemy.Boolean),
+    sqlalchemy.Column("duration", sqlalchemy.Integer),
+    sqlalchemy.Column("created_at", sqlalchemy.DateTime),
+    sqlalchemy.Column("summary", sqlalchemy.String, nullable=True),
+    sqlalchemy.Column("topics", sqlalchemy.JSON),
+    sqlalchemy.Column("events", sqlalchemy.JSON),
+    # with user attached, optional
+    sqlalchemy.Column("user_id", sqlalchemy.String),
+)
+
+engine = sqlalchemy.create_engine(
+    settings.DATABASE_URL, connect_args={"check_same_thread": False}
+)
+metadata.create_all(engine)
+
+
+async def database_connect():
+    await database.connect()
+
+
+async def database_disconnect():
+    await database.disconnect()
+
+
+subscribers_startup.append(database_connect)
+subscribers_shutdown.append(database_disconnect)