[docs] Missing explanations about the "id" field in the GridFilterModel

[alsiola]

Duplicates

• I have searched the existing issues

Latest version

• I have tested the latest version

Current behavior 😯

When creating a data grid with externally state-managed filterModel, opening the filter modal and adding a new filter (with "and") unsets the initial filter state.

Setting a property id (of any value) on the initial filter item seems to resolve the issue, but this is not documented and seems surprising.

{
    items: [
      {
        columnField: "commodity",
        operatorValue: "contains",
        value: "rice",
        id: 123 // <- adding this field resolves the issue
      }
    ]
  }

Screen.Recording.2021-09-29.at.09.52.41.mov

Expected behavior 🤔

Initial filter state should be maintained, or requirement for id property should be documented.

Steps to reproduce 🕹

Reproduced in CodeSandbox

Context 🔦

No response

Your environment 🌎

`npx @mui/envinfo`

  System:
    OS: macOS 11.6
  Binaries:
    Node: 14.16.0 - ~/.nvm/versions/node/v14.16.0/bin/node
    Yarn: 1.22.11 - ~/.nvm/versions/node/v14.16.0/bin/yarn
    npm: 6.14.11 - ~/.nvm/versions/node/v14.16.0/bin/npm
  Browsers:
    Chrome: 94.0.4606.61 (browser used to identify issue)
    Edge: Not Found
    Firefox: 84.0
    Safari: 14.1.2
  npmPackages:
    @emotion/react:  11.1.5 
    @emotion/styled:  10.0.27 
    @mui/x-data-grid: ^4.0.0 => 4.0.0 
    @types/react: ^17.0.0 => 17.0.0 
    react: 17.0.1 => 17.0.1 
    react-dom: 17.0.1 => 17.0.1 
    typescript: ^4.1.3 => 4.1.3 

Order ID 💳 (optional)

No response

[flaviendelangle]

https://mui.com/components/data-grid/filtering/#multi-column-filtering

Some of the demo descriptions are even wrong

As you said, if you have multiple filters, they should have an ID.

Here is the exact logic :

    if (props.filterModel !== undefined && props.filterModel.items.length > 1) {
      const hasItemsWithoutIds = props.filterModel.items.find((item) => item.id == null);
      if (hasItemsWithoutIds) {
        throw new Error(
          "The 'id' field is required on filterModel.items when you use multiple filters.",
        );
      }
    }