A little bit of guessing from my side. behind your page /csp/test/person.csp
there is a namespace  (eg. USER)  with DB user 
If you have no login page you run as "UnknownUser" 
If it has no access rights or appropriate roles (most likely) for this DB behind you are lost;

2 possible workarounds: 

  1. give "UnknownUser"  enough rights for this Namespace and/or DB. 
    • but this is then valid not just to this specific CSP page
    • not really recommendable
  2. create a new user with the required rights
    • on your CSP page you can assign this user undercover by method
    • %CSP.Session.Login() and you have PW under control
    • no need  to touch "UnknownUser"

with CSP you have a license user that can be changed by %CSP.Session.Login()

Login with this username and password, returns a status code to show if it worked or not. This method also trades license units at the same time so this CSP session will be logged in as a named user. If you pass type=1 then this will trade licenses only and not login as this user. After the login completes it also updates the property Username to match the $username value this session is logged in as. The property LicenseId is also updated to be the license identifier that this session is logged in with.
If a login fails then the property Username and property LicenseId will remain at their previous values. If you pass oldpassword then this will attempt to change the password of username from oldpassword to password and login as this user. Note new status return values: CSP applications can be two-factor-enabled. If the current application is one such, then if Login() successfully authenticates the username/password, it does not return $$$OK, but rather $$$CSPPendingTwoFactorAuthentication. During Two-Factor Authentication, an 8-character numeric security string will be sent to the user's cellphone. You must obtain this string from the user and call CompleteTwoFactorLogin^%CSP.Session() to complete authentication of this user. Also note that if the login SUCCEEDS (status returned will be $$$OK), but you were unable to secure a license, the new apperr parameter will have the value of $$$CSPErrorTradeLicense. In such a case, you may have to call the Login function again to trade a license. If you are calling merely to trade a license (type=1), then if the license trade fails, Login will return a status of $$$CSPErrorTradeLicense.

And that's the description

classmethod GenerateMappingFromXdata(class As %String, ByRef mapping) as %Status

Get the JSON adaptor configuration information from class and property parameters.

BUT:
https://docs.intersystems.com/iris20212/csp/documatic/%25CSP.Documatic.cls?&LIBRARY=%25SYS&CLASSNAME=%25JSON.Generator

This class is used internally by InterSystems IRIS. You should not make direct use of it within your applications. There is no guarantee made about either the behavior or future operation of this class.