server: accept OpenAI video_url content type and data: video URIs (#27921)

The OpenAI chat completions API specifies content part type "video_url"
with a {"url": ...} object, and clients typically send data: URIs
(e.g. data:video/mp4;base64,...). The llama-server only accepted the
non-standard "input_video" type and rejected data: URIs for video
(accept_base64_uri=false), so any OpenAI-conformant client failed with
"unsupported content[].type" or "Invalid uri format".

- accept "video_url" as an alias of "input_video"
- read the media object from whichever key was used
- allow data: URIs for video (data:video/*), as already done for images

tools/server/server-common.cpp

@@ -1263,12 +1263,13 @@ json oaicompat_chat_params_parse(
                 p["text"] = get_media_marker();
                 p.erase("input_audio");
 
-            } else if (type == "input_video") {
+            } else if (type == "input_video" || type == "video_url") {
                 if (!opt.allow_video) {
                     throw std::runtime_error("video input is not supported - hint: if this is unexpected, you may need to provide the mmproj");
                 }
 
-                json input_video = json_value(p, "input_video", json::object());
+                // accept the OpenAI-style "video_url" key as an alias of "input_video"
+                json input_video = json_value(p, type, json::object());
                 std::string url  = json_value(input_video, "data",
                                         json_value(input_video, "url", std::string()));
                 handle_media(out_files, url, opt.media_path);
@@ -1276,6 +1277,7 @@ json oaicompat_chat_params_parse(
                 p["type"] = "media_marker";
                 p["text"] = get_media_marker();
                 p.erase("input_video");
+                p.erase("video_url");
 
             } else if (type != "text") {
                 throw std::invalid_argument("unsupported content[].type");