Decorate async tests with @pytest.mark.asyncio

Without this, many tests fail in Python 3.14.0a2 because
`asyncio.get_event_loop()` no longer automatically starts an event loop,
instead raising a `RuntimeError` if there is no current event loop. See
https://docs.python.org/dev/library/asyncio-eventloop.html#asyncio.get_event_loop,
https://docs.python.org/dev/whatsnew/3.14.html#id3, and
python/cpython#126353.

tests/test_service.py

@@ -6,6 +6,7 @@
 
 
 class TestService:
+    @pytest.mark.asyncio
     @pytest.mark.parametrize(
         ('rate_limit', 'period'), ((1, 0.5), (3, 1.0), (100, 1.5))
     )
@@ -19,6 +20,7 @@ async def request(value: float):
             main = asyncio.gather(*[request(v) for v in range(int(rate_limit / period) + 100)])
             asyncio.get_event_loop().run_until_complete(main)
 
+    @pytest.mark.asyncio
     @pytest.mark.parametrize(
         ('max_simultaneous',), ((1,), (3,), (100,))
     )

tests/test_throttler.py

@@ -16,6 +16,7 @@ def test_exceptions(self, rate_limit: int, period: float):
         with pytest.raises(ValueError):
             Throttler(rate_limit, period)
 
+    @pytest.mark.asyncio
     @pytest.mark.parametrize(
         ('rate_limit', 'period', 'count'),
         tuple(product((1, 3, 5), (0.5, 1.0, 1.5), (3, 5, 7))) +

tests/test_throttler_simultaneous.py

@@ -7,6 +7,7 @@
 
 
 class TestThrottlerSimultaneous:
+    @pytest.mark.asyncio
     @pytest.mark.parametrize(
         ('max_simultaneous', 'count'), ((1, 10), (3, 10), (100, 500))
     )