# OpenAPI Webhooks

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps

  // scope specifies the scope of this rule.
  // Valid values are "Cluster", "Namespaced", and "*"
  // "Cluster" means that only cluster-scoped resources will match this rule.
  // Namespace API objects are cluster-scoped.
  // "Namespaced" means that only namespaced resources will match this rule.
  // "*" means that there are no scope restrictions.
  // Subresources match the scope of their parent resource.
  // Default is "*".
  //

OAuth2 was designed so that the backend or API could be independent of the server that authenticates the user.

But in this case, the same **FastAPI** application will handle the API and the authentication.

So, let's review it from that simplified point of view:

* The user types the `username` and `password` in the frontend, and hits `Enter`.

    Because of that, versions of FastAPI previous to 0.99.0 still used versions of OpenAPI lower than 3.1.0.

### Pydantic and FastAPI `examples`

  repeated string volumeLifecycleModes = 3;

  // storageCapacity indicates that the CSI volume driver wants pod scheduling to consider the storage
  // capacity that the driver deployment will report by creating
  // CSIStorageCapacity objects with capacity information, if set to true.
  //
  // The check can be enabled immediately when deploying a driver.
  // In that case, provisioning new volumes with late binding

## What is "Dependency Injection"

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

      // substitute an empty ImmutableSet to the user in place of this
      if (object instanceof CartesianSet) {
        CartesianSet<?> that = (CartesianSet<?>) object;
        return this.axes.equals(that.axes);
      }
      if (object instanceof Set) {
        Set<?> that = (Set<?>) object;
        return this.size() == that.size() && this.containsAll(that);
      }

  // Specifies the desired number of successfully finished pods the
  // job should be run with.  Setting to null means that the success of any
  // pod signals the success of all pods, and allows parallelism to have any positive
  // value.  Setting to 1 means that parallelism is limited to 1 and the success of that
  // pod signals the success of the job.
  // More info: https://kubernetes.io/docs/concepts/workloads/controllers/jobs-run-to-completion/

   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past
   * decade that assumes that they can use checkNotNull for non-precondition checks. I had hoped to

    This is the dataset that powers `HttpUrl.topPrivateDomain()`.

 *  Fix: Immediately update the connection's flow control window instead of waiting for the
    receiving stream to process it.

    This change may increase OkHttp's memory use for applications that make many concurrent HTTP
    calls and that can receive data faster than they can process it. Previously, OkHttp limited