Merge #21302: wallet: createwallet examples for descriptor wallets

5039e0e55a test: HelpExampleCliNamed and HelpExampleRpcNamed (Ivan Metlushko)
591735ef0b rpc: Add HelpExampleCliNamed and use it for `createwallet` doc (Wladimir J. van der Laan)
5d5a90e819 rpc: Add HelpExampleRpcNamed (Ivan Metlushko)

Pull request description:

  Rationale: make descriptor wallets more visible and just a bit easier to setup

  `bitcoin-cli help createwallet`

  **Before**:
  ```
  Examples:
  > bitcoin-cli createwallet "testwallet"
  > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createwallet", "params": ["testwallet"]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  ```

  **After**
  ```
  Examples:
  > bitcoin-cli createwallet "testwallet"
  > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createwallet", "params": ["testwallet"]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  > bitcoin-cli createwallet "descriptors" false false "" true true true
  > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createwallet", "params": ["descriptors", false, false, "", true, true, true]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  ```

ACKs for top commit:
  laanwj:
    Tested ACK 5039e0e55a

Tree-SHA512: d37210e6ce639addee881377092d8f6fb2a537a60a259c561899e24cf68a0254d7ff45a213573c938f626677e46770cd21113aae5974f26c66b9a2e137699c14

src/rpc/util.cpp

@@ -113,17 +113,80 @@ std::vector<unsigned char> ParseHexO(const UniValue& o, std::string strKey)
     return ParseHexV(find_value(o, strKey), strKey);
 }
 
+namespace {
+
+/**
+ * Quote an argument for shell.
+ *
+ * @note This is intended for help, not for security-sensitive purposes.
+ */
+std::string ShellQuote(const std::string& s)
+{
+    std::string result;
+    result.reserve(s.size() * 2);
+    for (const char ch: s) {
+        if (ch == '\'') {
+            result += "'\''";
+        } else {
+            result += ch;
+        }
+    }
+    return "'" + result + "'";
+}
+
+/**
+ * Shell-quotes the argument if it needs quoting, else returns it literally, to save typing.
+ *
+ * @note This is intended for help, not for security-sensitive purposes.
+ */
+std::string ShellQuoteIfNeeded(const std::string& s)
+{
+    for (const char ch: s) {
+        if (ch == ' ' || ch == '\'' || ch == '"') {
+            return ShellQuote(s);
+        }
+    }
+
+    return s;
+}
+
+}
+
 std::string HelpExampleCli(const std::string& methodname, const std::string& args)
 {
     return "> bitcoin-cli " + methodname + " " + args + "\n";
 }
 
+std::string HelpExampleCliNamed(const std::string& methodname, const RPCArgList& args)
+{
+    std::string result = "> bitcoin-cli -named " + methodname;
+    for (const auto& argpair: args) {
+        const auto& value = argpair.second.isStr()
+                ? argpair.second.get_str()
+                : argpair.second.write();
+        result += " " + argpair.first + "=" + ShellQuoteIfNeeded(value);
+    }
+    result += "\n";
+    return result;
+}
+
 std::string HelpExampleRpc(const std::string& methodname, const std::string& args)
 {
     return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
         "\"method\": \"" + methodname + "\", \"params\": [" + args + "]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
 }
 
+std::string HelpExampleRpcNamed(const std::string& methodname, const RPCArgList& args)
+{
+    UniValue params(UniValue::VOBJ);
+    for (const auto& param: args) {
+        params.pushKV(param.first, param.second);
+    }
+
+    return "> curl --user myusername --data-binary '{\"jsonrpc\": \"1.0\", \"id\": \"curltest\", "
+           "\"method\": \"" + methodname + "\", \"params\": " + params.write() + "}' -H 'content-type: text/plain;' http://127.0.0.1:8332/\n";
+}
+
 // Converts a hex string to a public key if possible
 CPubKey HexToPubKey(const std::string& hex_in)
 {