feat: allow grpc_set_header to set :authority (#61)

Author: spacewander

patch/1.21.4/nginx-grpc_set_header_authority.patch

@@ -0,0 +1,18 @@
+diff --git src/http/modules/ngx_http_grpc_module.c src/http/modules/ngx_http_grpc_module.c
+index 58332866..01c0f489 100644
+--- src/http/modules/ngx_http_grpc_module.c
++++ src/http/modules/ngx_http_grpc_module.c
+@@ -4621,6 +4621,13 @@ ngx_http_grpc_init_headers(ngx_conf_t *cf, ngx_http_grpc_loc_conf_t *conf,
+                 conf->host_set = 1;
+             }
+ 
++#if (NGX_HTTP_APISIX)
++            if (src[i].key.len == 10
++                && ngx_strncasecmp(src[i].key.data, (u_char *) ":authority", 10) == 0)
++            {
++                conf->host_set = 1;
++            }
++#endif
+             s = ngx_array_push(&headers_merged);
+             if (s == NULL) {
+                 return NGX_ERROR;