Make subject row in split screen sticky

frontend/src/app/features/work-packages/routing/wp-split-view/wp-split-view.html

@@ -8,7 +8,10 @@
 
       <wp-breadcrumb [workPackage]="workPackage"></wp-breadcrumb>
 
-      <edit-form [resource]="workPackage">
+      <edit-form
+        [resource]="workPackage"
+        class="work-packages--details-form"
+      >
         <div class="wp-show--header-container">
           <op-back-button *ngIf="showBackButton()"
                        linkClass="work-packages-back-button"

frontend/src/global_styles/layout/work_packages/_details_view.sass

@@ -76,15 +76,14 @@ body.router--work-packages-partitioned-split-view-new
     margin: .5rem .5rem 0 0
 
 .work-packages--details-content
+  display:         flex
+  flex-direction:  column
   position:        absolute
   top:             50px
   bottom:          55px
   width:           100%
-  overflow-x: hidden
-  overflow-y: scroll
-  padding:    0 5px 0 20px
-
-  @include styled-scroll-bar
+  overflow:        hidden
+  padding:         0 5px 10px 20px
 
 .work-packages--details
 
@@ -110,6 +109,16 @@ body.router--work-packages-partitioned-split-view-new
       padding: 5px 0 5px 5px
       font-size: 18px
 
+  .work-packages--details-form
+    display: flex
+    flex-direction: column
+    overflow: hidden
+
+  .work-package-details-tab
+    overflow-y: auto
+    overflow-x: hidden
+    @include styled-scroll-bar
+
 .work-packages--type-selector
   flex-shrink: 0