Cognito passes in explicitly null booleans for DefineAuth responses

[djrenren]

Another fun cognito issue cuz this service is wack sometimes:

When cognito passes in the response field of CognitoEventUserPoolsDefineAuthChallenge, it can look like so:

{
   "challengeName": null,
   "failAuthentication": null,
   "issueTokens": null
}

But the definition of CognitoEventUserPoolsDefineAuthResponse is:

aws-lambda-events/src/cognito/mod.rs

Lines 308 to 317 in 9b0c659

 #[derive(Clone, Debug, Default, Deserialize, Eq, PartialEq, Serialize)] 
 #[serde(rename_all = "camelCase")] 
 pub struct CognitoEventUserPoolsDefineAuthChallengeResponse { 
     #[serde(default)] 
     pub challenge_name: Option<String>, 
     #[serde(default)] 
     pub issue_tokens: bool, 
     #[serde(default)] 
     pub fail_authentication: bool, 
 } 

Serde does not use the default implementation if a value is explicitly set to null. It only uses default if the value is excluded. This results in a failure to deserialize. I'm currently working around this by using my own type defined with:

#[derive(Clone, Debug, Default, Deserialize, PartialEq, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct DefineAuthResponse{
    #[serde(default)]
    pub challenge_name: Option<String>,
    #[serde(default)]
    pub issue_tokens: Option<bool>,
    #[serde(default)]
    pub fail_authentication: Option<bool>,
}

But I'm not sure how Cognito handles the null values on the output. It may require them to be booleans.

[David Calavera]

But I'm not sure how Cognito handles the null values on the output. It may require them to be booleans.

No idea either. Feel free to open a PR with suggested changes.