Support single-quoted string literals in query parsing (#18)

* Support single-quoted string literals in query parsing

Add single-quoted string literal support to the NoSQL query parser,
matching Cosmos DB behavior where apostrophes are escaped by doubling
them (''). Includes parser unit tests and an API integration test.

Co-authored-by: Pijus Kamandulis <pikami@users.noreply.github.com>

* Use backslash escape for apostrophes in single-quoted strings

Cosmos DB escapes apostrophes with \' rather than SQL-style doubling.
Also fix EscapeCharacter to return proper values for \', \", and \\
which were previously producing empty substitutions.

Co-authored-by: Pijus Kamandulis <pikami@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

api/tests/documents_test.go

@@ -134,6 +134,34 @@ func Test_Documents(t *testing.T) {
 			)
 		})
 
+		t.Run("Should query document with single-quoted string literal", func(t *testing.T) {
+			testCosmosQuery(t, collectionClient,
+				`select c.id
+				FROM c
+				WHERE c.id='67890'
+				ORDER BY c.id`,
+				nil,
+				[]interface{}{
+					map[string]interface{}{"id": "67890"},
+				},
+			)
+		})
+
+		t.Run("Should query document with escaped single-quoted string literal", func(t *testing.T) {
+			ts.DataStore.CreateDocument(testDatabaseName, testCollectionName, map[string]interface{}{"id": "apostrophe-doc", "pk": "ap", "name": "it's"})
+
+			testCosmosQuery(t, collectionClient,
+				`select c.id
+				FROM c
+				WHERE c.name='it\'s'
+				ORDER BY c.id`,
+				nil,
+				[]interface{}{
+					map[string]interface{}{"id": "apostrophe-doc"},
+				},
+			)
+		})
+
 		t.Run("Should query document with query parameters", func(t *testing.T) {
 			testCosmosQuery(t, collectionClient,
 				`select c.id

parsers/nosql/nosql.peg

@@ -509,6 +509,8 @@ IntegerLiteral <- number:Integer {
 }
 StringLiteral <- "\"" chars:StringCharacter* "\"" {
     return parsers.Constant{Type: parsers.ConstantTypeString,Value: joinStrings(chars.([]interface{}))}, nil
+} / "'" chars:SingleQuotedStringCharacter* "'" {
+    return parsers.Constant{Type: parsers.ConstantTypeString,Value: joinStrings(chars.([]interface{}))}, nil
 }
 FloatLiteral <- [0-9]+"."[0-9]+ {
     floatValue, _ := strconv.ParseFloat(string(c.text), 64)
@@ -869,11 +871,14 @@ Integer <- [0-9]+ {
 StringCharacter <- !('"' / "\\") . { return string(c.text), nil }
   / "\\" seq:EscapeSequenceCharacter { return seq, nil }
 
+SingleQuotedStringCharacter <- !("'" / "\\") . { return string(c.text), nil }
+  / "\\" seq:EscapeSequenceCharacter { return seq, nil }
+
 EscapeSequenceCharacter <- char:EscapeCharacter
 
-EscapeCharacter <- "'"
-  / '"'
-  / "\\"
+EscapeCharacter <- "'" { return "'", nil }
+  / '"' { return "\"", nil }
+  / "\\" { return "\\", nil }
   / "b" { return "\b", nil }
   / "f" { return "\f", nil }
   / "n" { return "\n", nil }

parsers/nosql/were_test.go

@@ -149,6 +149,32 @@ func Test_Parse_Were(t *testing.T) {
 		)
 	})
 
+	t.Run("Should correctly parse single-quoted string literals", func(t *testing.T) {
+		testQueryParse(
+			t,
+			`SELECT c.id FROM c WHERE c.id = '12345' AND c.string = 'it\'s'`,
+			parsers.SelectStmt{
+				SelectItems: []parsers.SelectItem{{Path: []string{"c", "id"}}},
+				Table:       parsers.Table{SelectItem: testutils.SelectItem_Path("c")},
+				Filters: parsers.LogicalExpression{
+					Operation: parsers.LogicalExpressionTypeAnd,
+					Expressions: []interface{}{
+						parsers.ComparisonExpression{
+							Operation: "=",
+							Left:      parsers.SelectItem{Path: []string{"c", "id"}},
+							Right:     testutils.SelectItem_Constant_String("12345"),
+						},
+						parsers.ComparisonExpression{
+							Operation: "=",
+							Left:      parsers.SelectItem{Path: []string{"c", "string"}},
+							Right:     testutils.SelectItem_Constant_String("it's"),
+						},
+					},
+				},
+			},
+		)
+	})
+
 	t.Run("Should correctly parse NOT conditions", func(t *testing.T) {
 		testQueryParse(
 			t,