[predicates] ExpectedValuePredicate now accepts a dict parameter ``match_form_params`` and ``match_kwargs`` benefit from that. For instance, the following statements are valid:: __select__ = match_form_params('vid', 'subvid') __select__ = match_form_params(vid='list', subvid='incontext') __select__ = match_form_params(vid=('list', 'tsearch')) In the latter cases, not only the parameters (``vid``/``subvid``) must be in the request form but their corresponding value must also match the expected values (or one of possible choices if `values` is a sequence). closes #5484070

TACHES
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-- écrire objet stocke/manipule les données

-- extraire tests de chaîne de caractère

* utiliser sqlite 

* écrire fonction prend chemin en argument et renvoie contenu

* extraire tests (chaîne de caractère) de spec 

* utiliser yams pour schéma