spec: Describe how TokenDetails are detected

content/client-lib-development-guide/features.textile

@@ -1072,7 +1072,7 @@ h4. AuthOptions
 * @(AO1)@ A class providing configurable authentication options used when authenticating or issuing tokens explicitly. These options are used when invoking @Auth#authorize@, @Auth#requestToken@, @Auth#createTokenRequest@ and @Auth#authorize@
 * @(AO2)@ The attributes of @AuthOptions@ consist of:
 ** @(AO2a)@ @key@ string - Full Ably key string, as obtained from dashboard, used when signing token requests locally
-** @(AO2b)@ @authCallback@ - A callback to call to obtain a signed @TokenRequest@, @TokenDetails@ or a token string. This enables a client to obtain token requests or tokens from another entity, so tokens can be renewed without the client requiring a key. If a JSON-encodeable object is provided in the callback, then the library will determine if it's a @TokenRequest@ or @TokenDetails@ and use the @fromJson@ method ("TD7":#TD7, "TE6":#TE6) to construct an object
+** @(AO2b)@ @authCallback@ - A callback to call to obtain a signed @TokenRequest@, @TokenDetails@ or a token string. This enables a client to obtain token requests or tokens from another entity, so tokens can be renewed without the client requiring a key. If a JSON-encodable object is provided in the callback, then the library will determine if it's a @TokenDetails@ (if it contains a @token@ key) or @TokenRequest@ (no @token@ key) and use the @fromJson@ method ("TD7":#TD7, "TE6":#TE6) to construct an object
 ** @(AO2c)@ @authUrl@ string - A URL to query to obtain a signed @TokenRequest@, @TokenDetails@ or a token string. This enables a client to obtain token request or token from another entity, so tokens can be renewed without the client requiring a key
 ** @(AO2d)@ @authMethod@ - The HTTP verb to be used when a request is made by the library to the @authUrl@. Defaults to @GET@, supports @GET@ and @POST@
 ** @(AO2e)@ @authHeaders@ - Headers to be included in any request made by the library to the @authUrl@