fix #13150 Add uniqueModelMappings option

[bernie-schelberg-mywave]

Having multiple names for a model mapping can cause issues with clients that are expecting a particular types to always have the same model name. Refer #13150. Since this potentially breaks system that rely on having the class names work as mappings alongside custom discriminator values, a new configuration option has been added - uniqueModelMappings (defaults to false).

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[arandth]

To be honost: I don't see why we should need a new option for this. If this behavior is considered to be a bug, then it should be corrected without the need to set an new option.

[bernie-schelberg-mywave]

@arandth I'm happy to submit another that just fixes the issue, and doesn't add a new option, please advise if this is preferred.

[bernie-schelberg-mywave]

I opened another pull request which treats this issue as a bug and doesn't add the new configuration option: #13815. I'm happy to close this one if the other is preferred.

[bernie-schelberg-mywave]

Closing this one as the consensus seems to be that this is indeed a bug, and doesn't need another option to enable or disable the behaviour. Refer to #13815