feat(database): add noop mode with config flag and update related tests (#9054)

* test: enhance agent component tests and add new fixture for database-less sessions

- Added `use_noop_session` fixture to facilitate testing without a database.
- Expanded `TestAgentComponent` with new tests for agent responses using the Calculator tool and validation across all OpenAI and Anthropic models.
- Updated `test_component.py` to include tests for message sending without a database, ensuring proper event handling and message integrity.
- Refactored existing tests for clarity and consistency.

* fix: enhance user retrieval logic in get_or_create_super_user and teardown_superuser functions

- Updated user retrieval in both functions to handle different result types from the database query, ensuring robustness against unexpected return values.
- Added checks for `first()` method and list type to improve error handling and maintainability.

* feat: add support for no-op database operations in settings

- Introduced `use_noop_database` configuration option to disable all database operations, controlled by the `LANGFLOW_USE_NOOP_DATABASE` environment variable.
- Updated the `use_noop_session` fixture to reflect the new environment variable for testing without a database.

* feat: implement NoopSession for database-less operations

- Added NoopSession class to provide a no-operation database session, allowing for testing and operation without a real database connection.
- Updated DatabaseService to utilize NoopSession when the `use_noop_database` setting is enabled, ensuring all database operations are disabled in this mode.
- Enhanced error handling and logging for session management, improving robustness in scenarios where the database is not in use.

* refactor: update import paths for NoopSession in test files

- Changed import path for NoopSession from `langflow.services.database.service` to `langflow.services.database.session` in both `test_agent_component.py` and `test_component.py`.
- This refactor improves code organization and aligns with recent changes in the project structure.

* feat: enhance NoopSession with result handling methods

- Added an internal _NoopResult class to the NoopSession, providing methods `first()`, `all()`, and `one_or_none()` for better handling of no-operation results.
- This enhancement improves the usability of NoopSession in testing scenarios by mimicking expected database query behaviors.

* refactor: improve logging for NOOP database session

- Changed the log level from warning to info for the NOOP database session message in the DatabaseService class.
- This adjustment enhances clarity in logging, indicating that all DB operations are disabled without implying an error condition.

* docs: improve docstring formatting for custom_component_update function

- Reformatted the docstring for the custom_component_update function to enhance readability by breaking long lines into multiple lines.
- This change improves documentation clarity, making it easier for developers to understand the function's purpose and behavior.

* docs: add LANGFLOW_USE_NOOP_DATABASE environment variable documentation

- Introduced documentation for the new LANGFLOW_USE_NOOP_DATABASE environment variable, which allows users to enable a no-op database mode, avoiding database connections and operations.
- This addition enhances the clarity of configuration options available for Langflow, aiding users in understanding how to run flows without a database.

* refactor: move NOOP database session logging to settings

- Removed the logging statement from the DatabaseService class and added it to the `set_use_noop_database` field validator in the Settings class.
- This change centralizes the logging for the NOOP database session, improving code organization and ensuring that the message is logged whenever the setting is applied.

docs/docs/Configuration/environment-variables.mdx

@@ -194,6 +194,7 @@ The following table lists the environment variables supported by Langflow.
 | <Link id="LANGFLOW_COMPONENTS_PATH"/><span class="env-prefix">LANGFLOW_</span>COMPONENTS_PATH | String | `langflow/components` | Path to the directory containing custom components.<br/>See [`--components-path` option](./configuration-cli.mdx#run-components-path). |
 | <Link id="LANGFLOW_CONFIG_DIR"/><span class="env-prefix">LANGFLOW_</span>CONFIG_DIR | String | See description | Set the Langflow configuration directory where files, logs, and the Langflow database are stored. Defaults: **Linux/WSL**: `~/.cache/langflow/`<br/>**macOS**: `/Users/<username>/Library/Caches/langflow/`<br/>**Windows**: `%LOCALAPPDATA%\langflow\langflow\Cache`|
 | <Link id="LANGFLOW_DATABASE_URL"/><span class="env-prefix">LANGFLOW_</span>DATABASE_URL | String | Not set | Set the database URL for Langflow. If not provided, Langflow uses a SQLite database. |
+| <Link id="LANGFLOW_USE_NOOP_DATABASE"/><span class="env-prefix">LANGFLOW_</span>USE_NOOP_DATABASE | Boolean | `false` | Use a no-op database, which avoids database connections and operations. Useful for running flows without a database. |
 | <Link id="LANGFLOW_DATABASE_CONNECTION_RETRY"/><span class="env-prefix">LANGFLOW_</span>DATABASE_CONNECTION_RETRY | Boolean | `false` | If True, Langflow tries to connect to the database again if it fails. |
 | <Link id="LANGFLOW_DB_POOL_SIZE"/><span class="env-prefix">LANGFLOW_</span>DB_POOL_SIZE | Integer | `10` | **DEPRECATED:** Use <span class="env-prefix">LANGFLOW_</span>DB_CONNECTION_SETTINGS instead. The number of connections to keep open in the connection pool. |
 | <Link id="LANGFLOW_DB_MAX_OVERFLOW"/><span class="env-prefix">LANGFLOW_</span>DB_MAX_OVERFLOW | Integer | `20` | **DEPRECATED:** Use <span class="env-prefix">LANGFLOW_</span>DB_CONNECTION_SETTINGS instead. The number of connections to allow that can be opened beyond the pool size. |