feat(http1): add options to preserve header casing (#2480)

Decouple preserving header case from FFI:

The feature is now supported in both the server and the client
and can be combined with the title case feature, for headers
which don't have entries in the header case map.

Closes #2313

src/client/client.rs

@@ -997,6 +997,17 @@ impl Builder {
         self
     }
 
+    /// 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, val: bool) -> &mut Self {
+        self.conn_builder.h1_preserve_header_case(val);
+        self
+    }
+
     /// Set whether HTTP/0.9 responses should be tolerated.
     ///
     /// Default is false.

src/client/conn.rs

@@ -126,6 +126,7 @@ pub struct Builder {
     h09_responses: bool,
     h1_parser_config: ParserConfig,
     h1_title_case_headers: bool,
+    h1_preserve_header_case: bool,
     h1_read_buf_exact_size: Option<usize>,
     h1_max_buf_size: Option<usize>,
     #[cfg(feature = "http2")]
@@ -500,6 +501,7 @@ impl Builder {
             h1_read_buf_exact_size: None,
             h1_parser_config: Default::default(),
             h1_title_case_headers: false,
+            h1_preserve_header_case: false,
             h1_max_buf_size: None,
             #[cfg(feature = "http2")]
             h2_builder: Default::default(),
@@ -537,6 +539,11 @@ impl Builder {
         self
     }
 
+    pub(crate) fn h1_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 {
         self.h1_read_buf_exact_size = sz;
         self.h1_max_buf_size = None;
@@ -719,6 +726,9 @@ impl Builder {
                     if opts.h1_title_case_headers {
                         conn.set_title_case_headers();
                     }
+                    if opts.h1_preserve_header_case {
+                        conn.set_preserve_header_case();
+                    }
                     if opts.h09_responses {
                         conn.set_h09_responses();
                     }