Merge bitcoin/bitcoin#25760: rest: clean-up for mempool endpoints

acbea66 rest: clean-up for `mempool` endpoints (brunoerg)

Pull request description:

  The functions `rest_mempool_info` and `rest_mempool_contents` are similar, the only difference between them is:
  `rest_mempool_info` uses `MempoolInfoToJSON` to get the mempool informations and `rest_mempool_contents` uses `MempoolToJSON`, for this reason this PR creates a new function to handle it and reduce duplicated code.

  Also,
  1. Rename `strURIPart` to `str_uri_part`.
  2. Rename `strJSON` to `str_json`.

ACKs for top commit:
  stickies-v:
    re-ACK acbea66 - verified that just the error message was updated since bitcoin/bitcoin@da0c612
  theStack:
    re-ACK acbea66

Tree-SHA512: 35f6f0732a573fe8a6cdcc782f89ae3427a1de19f069a68c9c51bb525118c2b07e20303cbe19b9d4b7d1ad055d69c32def2d0fb8f886c851da562dd9ce33ad6a

Author: MacroFake

src/rest.cpp

@@ -590,45 +590,31 @@ static bool rest_chaininfo(const std::any& context, HTTPRequest* req, const std:
     }
 }
 
-static bool rest_mempool_info(const std::any& context, HTTPRequest* req, const std::string& strURIPart)
+static bool rest_mempool(const std::any& context, HTTPRequest* req, const std::string& str_uri_part)
 {
     if (!CheckWarmup(req))
         return false;
-    const CTxMemPool* mempool = GetMemPool(context, req);
-    if (!mempool) return false;
-    std::string param;
-    const RESTResponseFormat rf = ParseDataFormat(param, strURIPart);
-
-    switch (rf) {
-    case RESTResponseFormat::JSON: {
-        UniValue mempoolInfoObject = MempoolInfoToJSON(*mempool);
 
-        std::string strJSON = mempoolInfoObject.write() + "\n";
-        req->WriteHeader("Content-Type", "application/json");
-        req->WriteReply(HTTP_OK, strJSON);
-        return true;
-    }
-    default: {
-        return RESTERR(req, HTTP_NOT_FOUND, "output format not found (available: json)");
-    }
+    std::string param;
+    const RESTResponseFormat rf = ParseDataFormat(param, str_uri_part);
+    if (param != "contents" && param != "info") {
+        return RESTERR(req, HTTP_BAD_REQUEST, "Invalid URI format. Expected /rest/mempool/<info|contents>.json");
     }
-}
 
-static bool rest_mempool_contents(const std::any& context, HTTPRequest* req, const std::string& strURIPart)
-{
-    if (!CheckWarmup(req)) return false;
     const CTxMemPool* mempool = GetMemPool(context, req);
     if (!mempool) return false;
-    std::string param;
-    const RESTResponseFormat rf = ParseDataFormat(param, strURIPart);
 
     switch (rf) {
     case RESTResponseFormat::JSON: {
-        UniValue mempoolObject = MempoolToJSON(*mempool, true);
+        std::string str_json;
+        if (param == "contents") {
+            str_json = MempoolToJSON(*mempool, true).write() + "\n";
+        } else {
+            str_json = MempoolInfoToJSON(*mempool).write() + "\n";
+        }
 
-        std::string strJSON = mempoolObject.write() + "\n";
         req->WriteHeader("Content-Type", "application/json");
-        req->WriteReply(HTTP_OK, strJSON);
+        req->WriteReply(HTTP_OK, str_json);
         return true;
     }
     default: {
@@ -946,8 +932,7 @@ static const struct {
       {"/rest/blockfilter/", rest_block_filter},
       {"/rest/blockfilterheaders/", rest_filter_header},
       {"/rest/chaininfo", rest_chaininfo},
-      {"/rest/mempool/info", rest_mempool_info},
-      {"/rest/mempool/contents", rest_mempool_contents},
+      {"/rest/mempool/", rest_mempool},
       {"/rest/headers/", rest_headers},
       {"/rest/getutxos", rest_getutxos},
       {"/rest/blockhashbyheight/", rest_blockhash_by_height},