Let Security Schemes declare deprecation (OAI#2532)

Author: philsturgeon

src/oas.md

@@ -3817,6 +3817,7 @@ Please note that as of 2020, the implicit flow is about to be deprecated by [OAu
 | <a name="security-scheme-bearer-format"></a>bearerFormat | `string` | `http` (`"bearer"`) | A hint to the client to identify how the bearer token is formatted. Bearer tokens are usually generated by an authorization server, so this information is primarily for documentation purposes. |
 | <a name="security-scheme-flows"></a>flows | [OAuth Flows Object](#oauth-flows-object) | `oauth2` | **REQUIRED**. An object containing configuration information for the flow types supported. |
 | <a name="security-scheme-open-id-connect-url"></a>openIdConnectUrl | `string` | `openIdConnect` | **REQUIRED**. [Well-known URL](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfig) to discover the [[OpenID-Connect-Discovery]] [provider metadata](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata). |
+| <a name="security-scheme-deprecated"></a>deprecated | `boolean` | Declares this security scheme to be deprecated. Consumers SHOULD refrain from usage of the declared scheme. Default value is `false`. |
 
 This object MAY be extended with [Specification Extensions](#specification-extensions).