add docs

docs/en/docs/tutorial/query-params.md

@@ -223,3 +223,45 @@ In this case, there are 3 query parameters:
 
 !!! tip
     You could also use `Enum`s the same way as with [Path Parameters](path-params.md#predefined-values){.internal-link target=_blank}.
+
+## Free Form Query Parameters
+
+Sometimes you want to receive some query parameters, but you don't know in advance what they will be. **FastAPI** supports this case too.
+
+=== "Python 3.10+"
+
+    ```Python hl_lines="8"
+    {!> ../../../docs_src/query_params/tutorial007_py310.py!}
+    ```
+
+And when you open your browser at <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>, you will that OpenAPI supports this too:
+
+<img src="/img/tutorial/path-params/image01.png">
+
+However, since the query parameters are decaled in the request as 
+
+```
+http://127.0.0.1:8000/query/mixed-type-params?query=1&foo=bar&foo=baz
+```
+
+**FastAPI** greedily adds all the query parameters to every `Query` argument for which it is valid. The above request will be parsed as:
+
+```Python
+{
+  "query": 1,
+  "string_mapping": {
+    "query": "1",
+    "foo": "baz"
+  },
+  "mapping_query_int": {
+    "query": 1
+  },
+  "sequence_mapping_queries": {
+    "query": [
+      "1"
+    ],
+    "foo": []
+  }
+}
+```
+As you can see the `query` parameter is added to every `Query` argument for which it is valid. This is because **FastAPI** does not know which `Query` argument you want to add the `query` parameter to, and `1` validates as an `int`, `str`, and `List[str]`. `foo` is only added to the `string_mapping` and `sequence_mapping_queries` arguments because it is not a valid `int`.

docs_src/query_params/tutorial007_py310.py

@@ -0,0 +1,20 @@
+from typing import Mapping, List
+
+from fastapi import FastAPI, Query
+
+app = FastAPI()
+
+
+@app.get("/query/mixed-type-params")
+def get_mixed_mapping_mixed_type_query_params(
+    query: int = Query(),
+    mapping_query_str: Mapping[str, str] = Query({}),
+    mapping_query_int: Mapping[str, int] = Query({}),
+    sequence_mapping_queries: Mapping[str, List[int]] = Query({}),
+):
+    return {
+        "query":query, 
+        "string_mapping": mapping_query_str, 
+        "mapping_query_int": mapping_query_int, 
+        "sequence_mapping_queries": sequence_mapping_queries
+        }