feat(client): expose http09 and http1 options on client::conn::Builder (#2611)

These options are currently available on the high-level builder only.

Along the way, rename the setters to follow the public API conventions
and add docs.

Closes #2461

src/client/conn.rs

@@ -550,12 +550,34 @@ impl Builder {
         self
     }
 
-    pub(super) fn h09_responses(&mut self, enabled: bool) -> &mut Builder {
+    /// Set whether HTTP/0.9 responses should be tolerated.
+    ///
+    /// Default is false.
+    pub fn http09_responses(&mut self, enabled: bool) -> &mut Builder {
         self.h09_responses = enabled;
         self
     }
 
-    pub(crate) fn h1_allow_spaces_after_header_name_in_responses(
+    /// Set whether HTTP/1 connections will accept spaces between header names
+    /// and the colon that follow them in responses.
+    ///
+    /// You probably don't need this, here is what [RFC 7230 Section 3.2.4.] has
+    /// to say about it:
+    ///
+    /// > No whitespace is allowed between the header field-name and colon. In
+    /// > the past, differences in the handling of such whitespace have led to
+    /// > security vulnerabilities in request routing and response handling. A
+    /// > server MUST reject any received request message that contains
+    /// > whitespace between a header field-name and colon with a response code
+    /// > of 400 (Bad Request). A proxy MUST remove any such whitespace from a
+    /// > response message before forwarding the message downstream.
+    ///
+    /// Note that this setting does not affect HTTP/2.
+    ///
+    /// Default is false.
+    ///
+    /// [RFC 7230 Section 3.2.4.]: https://tools.ietf.org/html/rfc7230#section-3.2.4
+    pub fn http1_allow_spaces_after_header_name_in_responses(
         &mut self,
         enabled: bool,
     ) -> &mut Builder {
@@ -564,24 +586,51 @@ impl Builder {
         self
     }
 
-    pub(super) fn h1_title_case_headers(&mut self, enabled: bool) -> &mut Builder {
+    /// Set whether HTTP/1 connections will write header names as title case at
+    /// the socket level.
+    ///
+    /// Note that this setting does not affect HTTP/2.
+    ///
+    /// Default is false.
+    pub fn http1_title_case_headers(&mut self, enabled: bool) -> &mut Builder {
         self.h1_title_case_headers = enabled;
         self
     }
 
-    pub(crate) fn h1_preserve_header_case(&mut self, enabled: bool) -> &mut Builder {
+    /// Set whether HTTP/1 connections will write header names as provided
+    /// at the socket level.
+    ///
+    /// Note that this setting does not affect HTTP/2.
+    ///
+    /// Default is false.
+    pub fn http1_preserve_header_case(&mut self, enabled: bool) -> &mut Builder {
         self.h1_preserve_header_case = enabled;
         self
     }
 
-    pub(super) fn h1_read_buf_exact_size(&mut self, sz: Option<usize>) -> &mut Builder {
+    /// Sets the exact size of the read buffer to *always* use.
+    ///
+    /// Note that setting this option unsets the `http1_max_buf_size` option.
+    ///
+    /// Default is an adaptive read buffer.
+    pub fn http1_read_buf_exact_size(&mut self, sz: Option<usize>) -> &mut Builder {
         self.h1_read_buf_exact_size = sz;
         self.h1_max_buf_size = None;
         self
     }
 
+    /// Set the maximum buffer size for the connection.
+    ///
+    /// Default is ~400kb.
+    ///
+    /// Note that setting this option unsets the `http1_read_exact_buf_size` option.
+    ///
+    /// # Panics
+    ///
+    /// The minimum value allowed is 8192. This method panics if the passed `max` is less than the minimum.
     #[cfg(feature = "http1")]
-    pub(super) fn h1_max_buf_size(&mut self, max: usize) -> &mut Self {
+    #[cfg_attr(docsrs, doc(cfg(feature = "http1")))]
+    pub fn http1_max_buf_size(&mut self, max: usize) -> &mut Self {
         assert!(
             max >= proto::h1::MINIMUM_MAX_BUFFER_SIZE,
             "the max_buf_size cannot be smaller than the minimum that h1 specifies."