The RPC has serval methods regarding participants, all of them require a iTokenId in order to execute the desired query.

This can be useful because we can use these methods before a token has been assigned to the participant. (DB record is inserted with a blank token and updated later when a token is generated).

However, sometimes it can be useful to use the actual token (when it's available) instead of the tokenId.

Example:
We have a page, outside limesurvey in our own application, where a user can enter a token.
To be able to show information about the participant to which this token belongs to, we need to be able to call the RPC (get_participant_properties) with this token.
However, it's impossible using today's RPC due to only using the iTokenId.

A possible solution could be to add a new RPC method: get_participant_properties_by_token with the following code:
https://gist.github.com/frederikprijck/fe7580909eb6fb54ceecd857b609ca08

This code is a copy of the existing get_participant_properties, replacing a single line (https://github.com/LimeSurvey/LimeSurvey/blob/master/application/helpers/remotecontrol/remotecontrol_handle.php#L1646) with https://gist.github.com/frederikprijck/fe7580909eb6fb54ceecd857b609ca08#file-gistfile1-txt-L22

I don't like code duplication, so we need to figure a way to avoid code duplication without, possibly, impacting the existing get_participant_properties method.

Maybe there are other solutions? Feel free to discuss!