Migrate form_app to null safety (#925)

form_app/pubspec.lock

@@ -234,7 +234,7 @@ packages:
       name: http
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.2"
+    version: "0.13.4"
   http_multi_server:
     dependency: transitive
     description:
@@ -248,7 +248,7 @@ packages:
       name: http_parser
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.4"
+    version: "4.0.0"
   intl:
     dependency: "direct main"
     description:
@@ -319,13 +319,6 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.0.0"
-  mockito:
-    dependency: "direct main"
-    description:
-      name: mockito
-      url: "https://pub.dartlang.org"
-    source: hosted
-    version: "5.0.7"
   package_config:
     dependency: transitive
     description:
@@ -374,7 +367,7 @@ packages:
       name: shelf
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.7.9"
+    version: "1.2.0"
   shelf_web_socket:
     dependency: transitive
     description:
@@ -486,4 +479,4 @@ packages:
     source: hosted
     version: "3.1.0"
 sdks:
-  dart: ">=2.12.0 <3.0.0"
+  dart: ">=2.14.0 <3.0.0"