## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

```Python hl_lines="9-13  36-53"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip

// PolicyRule holds information that describes a policy rule, but does not contain information
// about who the rule applies to or which namespace the rule applies to.
message PolicyRule {
  // Verbs is a list of Verbs that apply to ALL the ResourceKinds contained in this rule. '*' represents all verbs.
  repeated string verbs = 1;

  // The list ordering isn't significant, may contain duplicates, and possibly be incomplete.
  repeated ResourceRule resourceRules = 1;

  // NonResourceRules is the list of actions the subject is allowed to perform on non-resources.
  // The list ordering isn't significant, may contain duplicates, and possibly be incomplete.
  repeated NonResourceRule nonResourceRules = 2;

| `contact` | `dict` | The contact information for the exposed API. It can contain several fields. <details><summary><code>contact</code> fields</summary><table><thead><tr><th>Parameter</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><code>name</code></td><td><code>str</code></td><td>The identifying name of the contact person/organization.</td></tr><tr><td><code>url</code></td><td><code>str</code></td><td>The...

  // If the signer cannot issue the certificate, a condition of type "Failed" is added and this field remains empty.
  //
  // Validation requirements:
  //  1. certificate must contain one or more PEM blocks.
  //  2. All PEM blocks must have the "CERTIFICATE" label, contain no headers, and the encoded data
  //   must be a BER-encoded ASN.1 Certificate structure as described in section 4 of RFC5280.

The new [ParseCookie] function parses a Cookie header value and
returns all the cookies which were set in it. Since the same cookie
name can appear multiple times the returned Values can contain
more than one value for a given key.

The new [ParseSetCookie] function parses a Set-Cookie header value and

// PolicyRule holds information that describes a policy rule, but does not contain information
// about who the rule applies to or which namespace the rule applies to.
message PolicyRule {
  // Verbs is a list of Verbs that apply to ALL the ResourceKinds contained in this rule. '*' represents all verbs.
  repeated string verbs = 1;

// PolicyRule holds information that describes a policy rule, but does not contain information
// about who the rule applies to or which namespace the rule applies to.
message PolicyRule {
  // Verbs is a list of Verbs that apply to ALL the ResourceKinds contained in this rule. '*' represents all verbs.
  repeated string verbs = 1;

Let's say you have a *path operation* with a path `/files/{file_path}`.

But you need `file_path` itself to contain a *path*, like `home/johndoe/myfile.txt`.

So, the URL for that file would be something like: `/files/home/johndoe/myfile.txt`.

### OpenAPI support

OpenAPI doesn't support a way to declare a *path parameter* to contain a *path* inside, as that could lead to scenarios that are difficult to test and define.

            display = ParameterDisplay.PROMPT,
            allowEmpty = false,
            description = "The name of the test to run, as should be passed to --tests. Can't contain spaces since there are problems with Teamcity's escaping, you can use * instead."
        )
        text(
            testJvmVersionParameter,
            JvmVersion.java11.major.toString(),