Allow filtering with "or" condition

[LIQRGV]

We should able transform this query param:
x_model?filter[x|y][is]=1&filter[z][in]=1,2,3

into this filter

...... where (x = 1 or y = 1) and z in (1,2,3);

[PMessinezis]

I would like to give it a try. I am thinking of the following approach :

1. in the constructor of FilterStruct : check if "|" is included in the fieldName, and if yes, then explode it into an array

2. in apply() method of FilterStruct : if fieldName is an array, then create a $subquery closure applying where/orWhere for the first and subsequent items in the fieldName array and then return $object->where($subquery)