Instruction: Explain how to implement and use signals in a Flask application.
Context: This question assesses the candidate's familiarity with Flask signals for event-driven programming, allowing actions to be triggered by certain events in the application.
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At the core, Flask signals allow us to decouple the execution of functions from the request-response cycle. This means we can execute code in response to certain events, such as when a new user signs up or a database entry is updated, without embedding the logic directly into our endpoint functions. This decoupling enhances our application's modularity and readability, which are critical for maintaining and scaling complex systems.
Implementing Flask signals starts with defining signal handlers. These handlers are functions that are connected to specific signals and are executed when those signals are emitted. For instance, if we're aiming to send a welcome email to each new user, we would first import the signal from Flask-Signals,...