apidash_core: contents moved into better_networking package

packages/better_networking/lib/extensions/map_extensions.dart

@@ -0,0 +1,37 @@
+import 'dart:io';
+
+extension MapExtension on Map {
+  bool hasKeyContentType() {
+    return keys.any(
+      (k) => (k is String)
+          ? k.toLowerCase() == HttpHeaders.contentTypeHeader
+          : false,
+    );
+  }
+
+  String? getKeyContentType() {
+    if (isEmpty) {
+      return null;
+    }
+    bool present = hasKeyContentType();
+    if (present) {
+      return keys.firstWhere(
+        (e) => (e is String)
+            ? e.toLowerCase() == HttpHeaders.contentTypeHeader
+            : false,
+      );
+    }
+    return null;
+  }
+
+  String? getValueContentType() {
+    return this[getKeyContentType()];
+  }
+
+  Map removeKeyContentType() {
+    removeWhere(
+      (key, value) => key.toLowerCase() == HttpHeaders.contentTypeHeader,
+    );
+    return this;
+  }
+}