strip charset name quotes

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index ae86b98..6bbf872 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -2632,7 +2632,17 @@
 
         r->headers_out.content_type_len = last - h->value.data;
 
-        r->headers_out.charset.len = h->value.data + h->value.len - p;
+        if (*p == '"') {
+            p++;
+        }
+
+        last = h->value.data + h->value.len;
+
+        if (*(last - 1) == '"') {
+            last--;
+        }
+
+        r->headers_out.charset.len = last - p;
         r->headers_out.charset.data = p;
 
         return NGX_OK;