📝 Update docs, add first tutorials

docs/tutorial/query-params.md

@@ -0,0 +1,177 @@
+When you declare other function parameters that are not part of the path parameters, they are automatically interpreted as "query" parameters.
+
+```Python hl_lines="9"
+{!./tutorial/src/query-params/tutorial001.py!}
+```
+
+The query is the set of key-value pairs that go after the `?` in a URL, separated by `&` characters.
+
+For example, in the url:
+
+```
+http://127.0.0.1:8000/items/?skip=0&limit=10
+```
+
+...the query parameters are:
+
+* `skip`: with a value of `0`
+* `limit`: with a value of `10`
+
+As they are part of the URL, they are "naturally" strings.
+
+But when you declare them with Python types (in the example above, as `int`), they are converted to that type and validated against it.
+
+All the same process that applied for path parameters also applies for query parameters:
+
+* Editor support (obviously)
+* Data <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>
+* Data validation
+* Automatic documentation
+
+## Defaults
+
+As query parameters are not a fixed part of a path, they can be optional and can have default values.
+
+In the example above they have default values of `skip=0` and `limit=10`.
+
+So, going to the URL:
+
+```
+http://127.0.0.1:8000/items/
+```
+
+would be the same as going to:
+
+```
+http://127.0.0.1:8000/items/?skip=0&limit=10
+```
+
+But if you go to, for example:
+
+```
+http://127.0.0.1:8000/items/?skip=20
+```
+
+The parameter values in your function will be:
+
+* `skip=20`: because you set it in the URL
+* `limit=10`: because that was the default value
+
+## Optional parameters
+
+The same way, you can declare optional query parameters, by setting their default to `None`:
+
+```Python hl_lines="7"
+{!./tutorial/src/query-params/tutorial002.py!}
+```
+
+In this case, the function parameter `q` will be optional, and will be `None` by default.
+
+!!! check
+    Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.
+
+## Query parameter type conversion
+
+You can also declare `bool` types, and they will be converted:
+
+```Python hl_lines="7"
+{!./tutorial/src/query-params/tutorial003.py!}
+```
+
+In this case, if you go to:
+
+```
+http://127.0.0.1:8000/items/?short=1
+```
+
+or
+
+```
+http://127.0.0.1:8000/items/?short=True
+```
+
+or
+
+```
+http://127.0.0.1:8000/items/?short=true
+```
+
+or
+
+```
+http://127.0.0.1:8000/items/?short=on
+```
+
+or
+
+```
+http://127.0.0.1:8000/items/?short=yes
+```
+
+or any other case variation (uppercase, first letter in uppercase, etc), your function will see the parameter `short` with a `bool` value of `True`. Otherwise as `False`.
+
+
+## Multiple path and query parameters
+
+You can declare multiple path parameters and query parameters at the same time, **FastAPI** knows which is which.
+
+And you don't have to declare them in any specific order.
+
+They will be detected by name:
+
+```Python hl_lines="6 8"
+{!./tutorial/src/query-params/tutorial004.py!}
+```
+
+## Required query parameters
+
+When you declare a default value for non-path parameters (for now, we have only seen query parameters), then it is not required.
+
+If you don't want to add a specific value but just make it optional, set the default as `None`.
+
+But when you want to make a query parameter required, you can just do not declare any default value:
+
+```Python hl_lines="6 8"
+{!./tutorial/src/query-params/tutorial005.py!}
+```
+
+Here the query parameter `needy` is a required query parameter of type `str`.
+
+If you open in your browser a URL like:
+
+```
+http://127.0.0.1:8000/users/2/items/foo-item
+```
+
+...without adding the required parameter `needy`, you will see an error like:
+
+```JSON
+{
+    "detail": [
+        {
+            "loc": [
+                "query",
+                "needy"
+            ],
+            "msg": "field required",
+            "type": "value_error.missing"
+        }
+    ]
+}
+```
+
+As `needy` is a required parameter, you would need to set it in the URL:
+
+```
+http://127.0.0.1:8000/users/2/items/foo-item?needy=sooooneedy
+```
+
+...this would work:
+
+```JSON
+{
+    "item_id": "foo-item",
+    "owner_id": 2,
+    "needy": "sooooneedy"
+}
+```