feat: Add SQLALCHEMY_MAX_OVERFLOW configuration to support database connection pool overflow (#24432)

docker/.env.example

 # The size of the database connection pool.
 # The default is 30 connections, which can be appropriately increased.
 SQLALCHEMY_POOL_SIZE=30
+# The default is 10 connections, which allows temporary overflow beyond the pool size.
+SQLALCHEMY_MAX_OVERFLOW=10
 # Database connection pool recycling time, the default is 3600 seconds.
 SQLALCHEMY_POOL_RECYCLE=3600
 # Whether to print SQL, default is false.

docker/docker-compose.yaml

   DB_PORT: ${DB_PORT:-5432}
   DB_DATABASE: ${DB_DATABASE:-dify}
   SQLALCHEMY_POOL_SIZE: ${SQLALCHEMY_POOL_SIZE:-30}
+  SQLALCHEMY_MAX_OVERFLOW: ${SQLALCHEMY_MAX_OVERFLOW:-10}
   SQLALCHEMY_POOL_RECYCLE: ${SQLALCHEMY_POOL_RECYCLE:-3600}
   SQLALCHEMY_ECHO: ${SQLALCHEMY_ECHO:-false}
   SQLALCHEMY_POOL_PRE_PING: ${SQLALCHEMY_POOL_PRE_PING:-false}