refactor(http): pass Server & Content-Length as proper headers

include/http/types.h

@@ -125,7 +125,9 @@ typedef enum http_header {
   http_header_connection = 0,
   http_header_location,
   http_header_content_type,
-  http_header_content_disposition
+  http_header_content_disposition,
+  http_header_server,
+  http_header_content_length
 } http_header;
 
 typedef enum http_body_type {

src/http/http_consts.c

@@ -97,7 +97,9 @@ const char *http_header_names[] = {
   "Connection",
   "Location",
   "Content-Type",
-  "Content-Disposition"
+  "Content-Disposition",
+  "Server",
+  "Content-Length"
 };
 
 const char *http_mime_type_names[][2] = {

src/http_loop/http_loop_res.c

@@ -1,10 +1,19 @@
 #include "http_loop.h"
 #include "log.h"
 
-// cppcheck-suppress syntaxError
-static const char *http_response_format = "HTTP/1.1 %i %s\n"
-                                          "Server: lander/" LANDER_VERSION "\n"
-                                          "Content-Length: %lu\n";
+static const char *server = "lander/" LANDER_VERSION;
+
+static int num_digits(size_t n) {
+  int digits = 1;
+
+  while (n > 9) {
+    digits++;
+
+    n /= 10;
+  }
+
+  return digits;
+}
 
 /*
  * This function precalculates the size of the total buffer required using
@@ -17,12 +26,20 @@ void http_loop_init_header(http_response *res) {
     res->status = http_ok;
   }
 
+  http_res_add_header(res, http_header_server, server, false);
+
+  char *content_length_header = malloc(num_digits(res->body.expected_len) + 1);
+  sprintf(content_length_header, "%zu", res->body.expected_len);
+
+  http_res_add_header(res, http_header_content_length, content_length_header,
+                      true);
+
   const char *response_type_name =
       http_status_names[res->status / 100 - 1][res->status % 100];
 
   // First we calculate the size of the start of the header
-  int buf_size = snprintf(NULL, 0, http_response_format, res->status,
-                          response_type_name, res->body.expected_len);
+  int buf_size =
+      snprintf(NULL, 0, "HTTP/1.1 %i %s\n", res->status, response_type_name);
 
   // We add each header's required size
   for (size_t i = 0; i < res->headers.len; i++) {
@@ -34,8 +51,7 @@ void http_loop_init_header(http_response *res) {
   // The + 1 is required to store the final null byte, but we will replace it
   // with the required final newline
   char *buf = malloc(buf_size + 1);
-  buf_size = sprintf(buf, http_response_format, res->status, response_type_name,
-                     res->body.expected_len);
+  buf_size = sprintf(buf, "HTTP/1.1 %i %s\n", res->status, response_type_name);
 
   for (size_t i = 0; i < res->headers.len; i++) {
     buf_size += sprintf(&buf[buf_size], "%s: %s\n",