Handle and track startup parameters (#478)

* User server parameters struct instead of server info bytesmut

* Refactor to use hashmap for all params and add server parameters to client

* Sync parameters on client server checkout

* minor refactor

* update client side parameters when changed

* Move the SET statement logic from the C packet to the S packet.

* trigger build

* revert validation changes

* remove comment

* Try fix

* Reset cleanup state after sync

* fix server version test

* Track application name through client life for stats

* Add tests

* minor refactoring

* fmt

* fix

* fmt

src/messages.rs

@@ -144,6 +144,10 @@ where
     bytes.put_slice(user.as_bytes());
     bytes.put_u8(0);
 
+    // Application name
+    bytes.put(&b"application_name\0"[..]);
+    bytes.put_slice(&b"pgcat\0"[..]);
+
     // Database
     bytes.put(&b"database\0"[..]);
     bytes.put_slice(database.as_bytes());
@@ -731,6 +735,21 @@ impl BytesMutReader for Cursor<&BytesMut> {
     }
 }
 
+impl BytesMutReader for BytesMut {
+    /// Should only be used when reading strings from the message protocol.
+    /// Can be used to read multiple strings from the same message which are separated by the null byte
+    fn read_string(&mut self) -> Result<String, Error> {
+        let null_index = self.iter().position(|&byte| byte == b'\0');
+
+        match null_index {
+            Some(index) => {
+                let string_bytes = self.split_to(index + 1);
+                Ok(String::from_utf8_lossy(&string_bytes[..string_bytes.len() - 1]).to_string())
+            }
+            None => return Err(Error::ParseBytesError("Could not read string".to_string())),
+        }
+    }
+}
 /// Parse (F) message.
 /// See: <https://www.postgresql.org/docs/current/protocol-message-formats.html>
 #[derive(Clone, Debug)]