Add support for nested fields filtering & Fix bug with null/'' dates

[pankgeorg]

With a different approach than remiremi, but inspired from his PR!

Feel free to close if you go another way!

[wiezmankimchi]

I tested and found this to be working as expected. There is only one change to the code need to be added to take care of an error: "Element does not exist" on the screen, or Error: expected a 32-bit integer for type "Int", but found a string. on the console.
This happens when the ID field in the db is Int while the buildGetListVariables build it with values as String. The change should be as follows:

const buildCreateVariables = (resource, aorFetchType, params, queryType) => {
  return params.data;
};

**// added to change cast for ID field from STRING to INT
const castIdType = (params, resource) => {
  const id = params.id
  const target = params.target

  if (!id) return

  const key = target ?? "id"
  const typedParam = resource.type.fields.find(f => key === f.name)
  if (!typedParam) return

  if (getFinalType(typedParam.type).name === "Int") {
    params[key] = parseInt(params[key])
  }
}**

  resource,
  aorFetchType,
  params,
  queryType
) => {
  **castIdType(params, resource)**
  switch (aorFetchType) {

This should change the cast of the ID field to the correct type.

[pankgeorg]

are you passing variables as 1234 or 1234?

[pankgeorg]

Adding a fix for this: marmelab/react-admin#6199