Removed deprecated APIs

Author: wilburx9

lib/src/api/service/api_service.dart

@@ -27,15 +27,14 @@ class ApiService {
 
       var statusCode = response.statusCode;
 
-      if (statusCode == HttpStatus.OK) {
+      if (statusCode == HttpStatus.ok) {
         Map<String, dynamic> responseBody = json.decode(body);
         completer.complete(TransactionApiResponse.fromMap(responseBody));
       } else {
         completer.completeError('charge transaction failed with status code: '
             '$statusCode and response: $body');
       }
     } catch (e) {
-
       completer.completeError('charge transaction failed error: $e');
     }
 
@@ -53,15 +52,14 @@ class ApiService {
       var body = response.body;
 
       var statusCode = response.statusCode;
-      if (statusCode == HttpStatus.OK) {
+      if (statusCode == HttpStatus.ok) {
         Map<String, dynamic> responseBody = json.decode(body);
         completer.complete(TransactionApiResponse.fromMap(responseBody));
       } else {
         completer.completeError('validate charge transaction failed with '
             'status code: $statusCode and response: $body');
       }
     } catch (e) {
-
       completer.completeError('validate charge transaction failed error: $e');
     }
 
@@ -75,15 +73,14 @@ class ApiService {
       http.Response response = await http.get(url, headers: headers);
       var body = response.body;
       var statusCode = response.statusCode;
-      if (statusCode == HttpStatus.OK) {
+      if (statusCode == HttpStatus.ok) {
         Map<String, dynamic> responseBody = json.decode(body);
         completer.complete(TransactionApiResponse.fromMap(responseBody));
       } else {
         completer.completeError('requery transaction failed with status code: '
             '$statusCode and response: $body');
       }
     } catch (e) {
-
       completer.completeError('requery transaction failed error: $e');
     }