add mysql support

api/kiwi_vpn_api/config.py

@@ -32,15 +32,38 @@ class DBType(Enum):
 
 
 class DBConfig(BaseModel):
-    db_type: DBType = DBType.sqlite
+    type: DBType = DBType.sqlite
+    user: str | None = None
+    password: str | None = None
+    host: str | None = None
+    database: str | None = "./tmp/vpn.db"
+
+    mysql_driver: str = "pymysql"
+    mysql_args: list[str] = ["charset=utf8mb4"]
 
     @property
     async def db_engine(self) -> Engine:
+        if self.type is DBType.sqlite:
+            # SQLite backend
             return create_engine(
-            "sqlite:///./tmp/vpn.db",
+                f"sqlite:///{self.database}",
                 connect_args={"check_same_thread": False},
             )
 
+        elif self.type is DBType.mysql:
+            # MySQL backend
+            if self.mysql_args:
+                args_str = "?" + "&".join(self.mysql_args)
+            else:
+                args_str = ""
+
+            return create_engine(
+                f"mysql+{self.mysql_driver}://"
+                f"{self.user}:{self.password}@{self.host}"
+                f"/{self.database}{args_str}",
+                pool_recycle=3600,
+            )
+
 
 class JWTConfig(BaseModel):
     secret: str | None = None