Adds the calling class to the string for the ajax hash to prevent collisions

[mslinnea]

Addresses #621

[dlh01]

🌳 I wondered whether the post, term, and user datasources should get the same fix, since they override the default get_ajax_action(). But I see that each has a distinct leading string like fm_datasource_post and fm_datasource_term...except for the user datasource, which also uses fm_datasource_post (oops!). Can we switch that to fm_datasource_user while we're here? (Or drop the _type_ prefix from each and use get_called_class() like in the parent class.)

[mboynes]

except for the user datasource, which also uses fm_datasource_post

😆

[mslinnea]

@dlh01 I updated the other classes to all use get_called_class() since that will prevent this same issue if those classes were extended.

[dlh01]

@mslinnea Unfortunately, it seems that using get_called_class() on its own will cause datasources to break when the class name is under a namespace: The action name in $_POST will get slashed and will no longer match the action name generated by Fieldmanager, like \\My\\Datasource instead of \My\Datasource.

I'm wondering whether the class name should be part of the hashed string instead, so maybe fm_datasource_{$hash}.

[mslinnea]

@dlh01 Valid point, I've updated these so that the called class is part of the hash, and I also fixed the preface for the user datasource.

[dlh01]

🌳 Now we're cookin' with get_called_class()!