fix: add flow name (authorizationCode) for OAuth2 example

[alukach]

The flows object should be a mapping of string to flow object, as per:

authentication/README.md

Lines 66 to 82 in faa9897

	### Authentication Scheme Object
	The Authentication Scheme extends the
	[OpenAPI security spec](https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#security-scheme-object)
	for support of OAuth2.0, API Key, and OpenID Connect authentication.
	All the [authentication clients](https://github.com/stac-utils/stac-asset#clients) included in the
	[stac-asset](https://github.com/stac-utils/stac-asset)
	library can be described, as well as a custom signed URL authentication scheme.
	| Field Name | Type | Applies to | Description |
	| ------------------ | ------------------------------------------------------------ | --------------------- | ------------------------------------------------------------ |
	| `type` | string | *All* | **REQUIRED**. The authentication scheme type used to access the data (`http` \| `s3` \| `signedUrl` \| `oauth2` \| `apiKey` \| `openIdConnect` \| a custom scheme type ). |
	| `description` | string | *All* | Additional instructions for authentication. [CommonMark 0.29](https://commonmark.org/) syntax MAY be used for rich text representation. |
	| `name` | string | `apiKey` | **REQUIRED.** The name of the header, query, or cookie parameter to be used. |
	| `in` | string | `apiKey` | **REQUIRED.** The location of the API key (`query` \| `header` \| `cookie`). |
	| `scheme` | string | `http` | **REQUIRED.** The name of the HTTP Authorization scheme to be used in the [Authorization header as defined in RFC7235](https://tools.ietf.org/html/rfc7235#section-5.1). The values used SHOULD be registered in the [IANA Authentication Scheme registry](https://www.iana.org/assignments/http-authschemes/http-authschemes.xhtml). (`basic` \| `bearer` \| `digest` \| `dpop` \| `hoba` \| `mutual` \| `negotiate` \| `oauth` (1.0) \| `privatetoken` \| `scram-sha-1` \| `scram-sha-256` \| `vapid`) |
	| `flows` | Map<string, ([OAuth2 Flow Object](#oauth2-flow-object)\|[Signed URL Object](#signed-url-object))> | `oauth2`, `signedUrl` | **REQUIRED.** Scenarios an API client performs to get an access token from the authorization server. For `oauth2` the following keys are pre-defined for the corresponding OAuth flows: `authorizationCode` \| `implicit` \| `password ` \| `clientCredentials`. The OAuth2 Flow Object applies for `oauth2`, the Signed URL Object applies to `signedUrl`. |

Relates to #41