Feature/search after before on (#9219)

* initial implementation of after, before, on search flags allowing to restrict the search to a specific day or a date range

* missed setting beforeDate in SearchParams in one place

* fixed condition when only flags are used for search without any plain terms

* changed date format used for after/before/on flags to be in ISO8601 format as suggested in PR comments, added a helper function to pad month and day with zeroes allowing the user user either format, with or without leading zeroes

* corrected expected compare to date setting for the TestParseDateFilterToTimeISO8601 test

* fixed a bug for the scenario when you only have the date flags without any terms, added a couple of tests for that scenario

* updated the date filter logic to use parameters to construct the query instead of simply appending strings together, as suggested in the pull request comments

* added search unit test using date flags

* added a helper function to create a test post with a createat date manually set, updated the test for search using date flags to create test posts with different createat dates to be able to better test the functionality

* MM-11817 Add support for after/before/on search flags with Elasticsearch

* add support to search posts to perform the search in context of the client's timezone when filtering by createat date using on: after: before: flags

* updated tests to match the new signature

model/utils.go

@@ -148,6 +148,46 @@ func GetMillis() int64 {
 	return time.Now().UnixNano() / int64(time.Millisecond)
 }
 
+// GetMillisForTime is a convience method to get milliseconds since epoch for provided Time.
+func GetMillisForTime(thisTime time.Time) int64 {
+	return thisTime.UnixNano() / int64(time.Millisecond)
+}
+
+// ParseDateFilterToTime is a convience method to get Time from string
+func ParseDateFilterToTime(filterString string) time.Time {
+	resultTime, err := time.Parse("2006-01-02", PadDateStringZeros(filterString))
+	if err != nil {
+		return time.Now()
+	}
+	return resultTime
+}
+
+// PadDateStringZeros is a convience method to pad 2 digit date parts with zeros to meet ISO 8601 format
+func PadDateStringZeros(dateString string) string {
+	parts := strings.Split(dateString, "-")
+	for index, part := range parts {
+		if len(part) == 1 {
+			parts[index] = "0" + part
+		}
+	}
+	dateString = strings.Join(parts[:], "-")
+	return dateString
+}
+
+// GetStartOfDayMillis is a convience method to get milliseconds since epoch for provided date's start of day
+func GetStartOfDayMillis(thisTime time.Time, timeZoneOffset int) int64 {
+	localSearchTimeZone := time.FixedZone("Local Search Time Zone", timeZoneOffset)
+	resultTime := time.Date(thisTime.Year(), thisTime.Month(), thisTime.Day(), 0, 0, 0, 0, localSearchTimeZone)
+	return GetMillisForTime(resultTime)
+}
+
+// GetEndOfDayMillis is a convience method to get milliseconds since epoch for provided date's end of day
+func GetEndOfDayMillis(thisTime time.Time, timeZoneOffset int) int64 {
+	localSearchTimeZone := time.FixedZone("Local Search Time Zone", timeZoneOffset)
+	resultTime := time.Date(thisTime.Year(), thisTime.Month(), thisTime.Day(), 23, 59, 59, 999999999, localSearchTimeZone)
+	return GetMillisForTime(resultTime)
+}
+
 func CopyStringMap(originalMap map[string]string) map[string]string {
 	copyMap := make(map[string]string)
 	for k, v := range originalMap {