Make the retro compatible if no top_n will return

all results

here is a script to make some test

```script

URL=${1:-http://127.0.0.1:8181}

curl "$URL/v1/rerank" -H "Content-Type: application/json" \
 -d '{ "model": "M", "query": "What is the recipe to make bread ?",
 "return_text" : true,
 "texts" : true,
 "top_n": 6,
 "documents": [
 "voici la recette pour faire du pain, il faut de la farine de l eau et du levain et du sel",
 "it is a bear",
 "bread recipe : floor, water, yest, salt",
 "The giant panda (Ailuropoda melanoleuca), sometimes called a panda bear or simply panda, is a bear species endemic to China.",
 "here is the ingedients to bake bread : 500g floor, 350g water, 120g fresh refresh yest, 15g salt",
 "recipe to make cookies : floor, eggs, water, chocolat",
 "here is the recipe to make bread : 500g floor, 350g water, 120g fresh refresh yest, 15g salt",
 "il fait tres beau aujourd hui",
 "je n ai pas faim, je ne veux pas manger",
 "je suis a paris"
 ] }' | jq
```

Author: YannFollet

tools/server/server.cpp

@@ -5060,15 +5060,6 @@ int main(int argc, char ** argv) {
 
         const json body = json::parse(req.body);
 
-        // TODO: implement
-        int top_n = 1;
-        if (body.count("top_n") == 1) {
-            top_n = body.at("top_n");
-        } else {
-            res_error(res, format_error_response("\"top_n\" must be provided", ERROR_TYPE_INVALID_REQUEST));
-            return;
-        }
-
         // if true, use TEI API format, otherwise use Jina API format
         // Jina: https://jina.ai/reranker/
         // TEI: https://huggingface.github.io/text-embeddings-inference/#/Text%20Embeddings%20Inference/rerank
@@ -5093,6 +5084,11 @@ int main(int argc, char ** argv) {
             return;
         }
 
+        int top_n = documents.size(); // no top_n will return all the documents
+        if (body.count("top_n") == 1) {
+            top_n = body.at("top_n");
+        }
+
         // create and queue the task
         json responses = json::array();
         bool error = false;