The `header::Formatter` ensures that a formatted header is written to a
line, and allows for headers that require multiple lines. The only
header to specifically require this is `Set-Cookie`.
BREAKING CHANGE: The `fmt_header` method has changed to take a different
formatter. In most cases, if your header also implements
`fmt::Display`, you can just call `f.fmt_line(self)`.
Change the internal representation of Origin to be more allocator
friendly. The internals of the Origin header are now private to allow
changing them in the future.
BREAKING CHANGES:
- Old code that accesses the Origin struct directly will stop working.
BREAKING CHANGE: The `Preference` header had a typo in a variant and it's string representation,
change `Preference::HandlingLeniant` to `Preference::HandlingLenient`.
This allows us to improve the performance. For now, a Cow is used
internally, so clients can set the host to a static value and no longer
need copies.
Later, we can change it to also possibly have a MemSlice.
BREAKING CHANGE: The fields of the `Host` header are no longer
available. Use the getter methods instead.
The Raw type repesents the raw bytes of a header-value.
Having a special type allows a couple of benefits:
- The exact representation has become private, allowing "uglier"
internals. Specifically, since the common case is for a header to only
have 1 line of bytes, an enum is used to skip allocating a Vec for only
1 line. Additionally, a Cow<'static, [u8]> is used, so static bytes
don't require a copy. Finally, since we can use static bytes, when
parsing, we can compare the incoming bytes against a couple of the most
common header-values, and possibly remove another copy.
- As its own type, the `Headers.set_raw` method can be generic over
`Into<Raw>`, which allows for more ergnomic method calls.
BREAKING CHANGE: `Header::parse_header` now receives `&Raw`, instead of
a `&[Vec<u8>]`. `Raw` provides several methods to ease using it, but
may require some changes to existing code.
