Support Sequence[Tuple[str, str]] type when setting cookies.

[tomchristie]

For consistency, we should support styles like: cookies=[('name', 'value')].

We allow either dicts or lists-of-tuples for each of data, files, params & headers, so it makes sense for us to do it here too.

[tomchristie]

We'd want to adjust the __init__ to handle that case properly...

httpx/httpx/_models.py

Line 1045 in 15c1e42

if cookies is None or isinstance(cookies, dict):

And adjust the type signature...

httpx/httpx/_types.py

Line 48 in 15c1e42

CookieTypes = Union["Cookies", CookieJar, Dict[str, str]]

Plus add a test case for it in here... https://github.com/encode/httpx/blob/master/tests/models/test_cookies.py
I guess use something like this...

cookies = httpx.Cookies([("key1", "value1"), ("key2", "value2")])
# followed by some appropriate assertions, similar to those in `test_cookies`.

Ideally do this in two commits - first add the (failing) test case, and then add the fixes.

[tomchristie]

Closed via #1211