Change json serialization behavior to ignore null

[henrik-me]

Is your feature request related to a problem? Please describe.
For certain older auth libraries there is an issue with null handling in json thus we should move to not adding fields which values is null. Especially important is the handling of foci_id.

Describe the solution you'd like
Ensure the json serializer doesn't write values to the json for which the values are null.

Describe alternatives you've considered
N/A

Additional context
https://stackoverflow.com/questions/6507889/how-to-ignore-a-property-in-class-if-null-using-json-net

[jmprieur]

@MarkZuber : I believe this is fixed?

[MarkZuber]

Yes. It’s fixed.

…

________________________________ From: Jean-Marc Prieur <[email protected]> Sent: Friday, June 14, 2019 4:01:16 AM To: AzureAD/microsoft-authentication-library-for-dotnet Cc: Mark Zuber; Mention Subject: Re: [AzureAD/microsoft-authentication-library-for-dotnet] Change json serialization behavior to ignore null (#1189) @MarkZuber<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMarkZuber&data=02%7C01%7CMark.Zuber%40microsoft.com%7C6a0a94da4b9a49a4964d08d6f0b79fce%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636961068787008767&sdata=31l1XpS7M98lDtbWoWHWKVkL40IVXcsYaCHb87Zea4c%3D&reserved=0> : I believe this is fixed? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FAzureAD%2Fmicrosoft-authentication-library-for-dotnet%2Fissues%2F1189%3Femail_source%3Dnotifications%26email_token%3DABWGFSVBJUATHRN4J2FLBBTP2N27ZA5CNFSM4HR6XWFKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODXWOZKQ%23issuecomment-502066346&data=02%7C01%7CMark.Zuber%40microsoft.com%7C6a0a94da4b9a49a4964d08d6f0b79fce%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636961068787018762&sdata=f1z0aWQQ66eQaEbSSHY%2BXp4jOMmYbfLMoZp%2F8xY8sW8%3D&reserved=0>, or mute the thread<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fnotifications%2Funsubscribe-auth%2FABWGFSSB22MK6GCXZ2YJVQLP2N27ZANCNFSM4HR6XWFA&data=02%7C01%7CMark.Zuber%40microsoft.com%7C6a0a94da4b9a49a4964d08d6f0b79fce%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636961068787028757&sdata=%2FWfI3lWO3Ip7%2FIaEfC1ZMjh4lPuoy%2FbLJWt%2FKZx40h8%3D&reserved=0>.

[jmprieur]

this is now fixed and available in MSAL.NET 4.1