feat(client): add conn::Builder::max_buf_size()

This allows users to configure a limit to client connections' read and
write buffers.

Closes #1748

src/client/mod.rs

@@ -901,6 +901,8 @@ impl 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.
     #[inline]
     pub fn http1_read_buf_exact_size(&mut self, sz: usize) -> &mut Self {
@@ -908,6 +910,21 @@ impl Builder {
         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.
+    #[inline]
+    pub fn http1_max_buf_size(&mut self, max: usize) -> &mut Self {
+        self.conn_builder.h1_max_buf_size(max);
+        self
+    }
+
     /// Set whether HTTP/1 connections will write header names as title case at
     /// the socket level.
     ///