Test mandatory columns for missing values and fail on error - enhanced

<p>This workflow processes a series of columns in which the first row indicates if the column is mandatory or optional.</p><p></p><p>If a column is mandatory and contains any missing values, the workflow stops processing, with an error message.<br><br>This workflow demonstrates the Java Snippet's "throw Abort("message");<br><br>which will return a message to the UI and halt processing.</p><p></p><p><strong>Enhanced version which optimises "discovery" of missing values by counting the number of non-missing values in each column and then only presenting those columns to the Column List Loop, which is now a "convenience" loop as it will abort on the first column.</strong></p><p></p><p>@takbb Brian Bates 06 November 2024</p>