refactor: Add FlightSchedule.Index field and update parsers

The code changes introduce a new `Index` field in the `FlightSchedule` struct and update the parsers in `aviation_parser.go` and `schedule_parser.go` to handle this field. This addition allows for the extraction and parsing of the `Index` value from flight schedule messages. The changes improve the functionality and accuracy of the code when working with flight schedules.

internal/parsers/aviation_parser.go

@@ -51,6 +51,7 @@ const (
 	PerformanceCategory  = "per"
 	RerouteInformation   = "rif"
 	Remarks              = "remark"
+	Index                = "idx"
 )
 
 var (
@@ -105,8 +106,11 @@ func (bp *BodyParser) Parse() (string, interface{}, error) {
 
 	if patternConfig, exists := bp.bodyPatterns[category]; exists && patternConfig.Patterns != nil {
 		for _, p := range patternConfig.Patterns {
-			if match := p.Expression.FindStringSubmatch(bp.body); match != nil {
-				data := extractData(match, p.Expression)
+			// if match := p.Expression.FindStringSubmatch(bp.body); match != nil {
+			// 	data := extractData(match, p.Expression)
+			// 	return bp.createBodyData(data)
+			// }
+			if data := parse(bp.body, p.Expression); data != nil {
 				return bp.createBodyData(data)
 			}
 		}
@@ -125,6 +129,14 @@ func findCategory(body string) string {
 	return ""
 }
 
+func parse(data string, exp *regexp.Regexp) map[string]string {
+	match := exp.FindStringSubmatch(data)
+	if len(match) > 0 {
+		return extractData(match, exp)
+	}
+	return nil
+}
+
 func extractData(match []string, re *regexp.Regexp) map[string]string {
 	data := make(map[string]string)
 	for i, name := range re.SubexpNames() {