Painless script implementation (PEG edition) (#1064)

This PR adds a rudimentary implementation of the Painless script. This
is the first usage of the "PEG" parser.

Author: nablaone

quesma/model/query.go

@@ -3,6 +3,7 @@
 package model
 
 import (
+	"quesma/painful"
 	"quesma/schema"
 	"time"
 )
@@ -85,9 +86,10 @@ type (
 
 // RuntimeMapping is a mapping of a field to a runtime expression
 type RuntimeMapping struct {
-	Field string
-	Type  string
-	Expr  Expr
+	Field                 string
+	Type                  string
+	DatabaseExpression    Expr
+	PostProcessExpression painful.Expr
 }
 
 const MainExecutionPlan = "main"

quesma/painful/.gitattributes

@@ -0,0 +1,5 @@
+
+# Mark *.go files as generated
+# https://github.com/github-linguist/linguist/blob/master/docs/overrides.md
+
+generated_parser.go linguist-generated