The first path segment is unexpectedly interpreted as an authority after normalization

• scheme:/..///bar has scheme="scheme", authority=None, path=/..///bar.
  However, after normalization, it has scheme="scheme", authority="bar".
• Consider t1 as an IRI ..///bar resolved against scheme:.
  t1 should have scheme="scheme" and authority=None (since ..///bar does not contain authority).
  However, resulting string is scheme://bar, it has authority=bar.

And some more examples:

$ python
Python 3.9.9 (main, Jan 10 2022, 18:52:39)
[GCC 11.2.1 20211127] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from rfc3986 import uri_reference
>>> b = uri_reference('scheme:')
>>> r1 = uri_reference('..///bar')
>>> t1 = r1.resolve_with(b)
>>> t1
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> t1.unsplit()
'scheme://bar'
>>> r2 = uri_reference('/..///bar')
>>> r2.resolve_with(b)
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> uri_reference('scheme:/..///bar').normalize()
URIReference(scheme='scheme', authority=None, path='//bar', query=None, fragment=None)
>>> uri_reference('scheme:/..///bar').normalize().unsplit()
'scheme://bar'

I'm not sure how this should handled.
Collapsing the // at the beginning is not explicitly allowed by RFC 3986, so I think the normalization and the resolution cannot produce valid output and should fail in this case.
(But RFC 3986 does not seem to state that they can fail!)

This can caused by normalization during resolution, so #84 may also be affected by this issue.

从 uri_reference() 入口开始，结合 issue 中的示例以及其中引用的 RFC 3986 规则，跟踪 normalize()、resolve_with() 和 unsplit()。确定在不存在 authority 时应如何处理开头的双斜杠，包括与 issue #84 中所指出的交互。完成的标准是：预期行为已得到明确规定，并且示例不再将第一个路径段重新解释为 authority。