Support for prepared statements (#474)

* Start prepared statements

* parse

* Ok

* optional

* dont rewrite anonymous prepared stmts

* Dont rewrite anonymous prep statements

* hm?

* prep statements

* I see!

* comment

* Print config value

* Rewrite bind and add sqlx test

* fmt

* ok

* Fix

* Fix stats

* its late

* clean up PREPARE

src/errors.rs

@@ -26,6 +26,7 @@ pub enum Error {
     AuthPassthroughError(String),
     UnsupportedStatement,
     QueryRouterParserError(String),
+    QueryRouterError(String),
 }
 
 #[derive(Clone, PartialEq, Debug)]
@@ -121,3 +122,9 @@ impl std::fmt::Display for Error {
         }
     }
 }
+
+impl From<std::ffi::NulError> for Error {
+    fn from(err: std::ffi::NulError) -> Self {
+        Error::QueryRouterError(err.to_string())
+    }
+}