Add a metadata contains operator

js/filterbar.js

@@ -298,7 +298,8 @@ class MetadataValueFilter extends Filter {
         gt: '>',
         lt: '<',
         gte: '>=',
-        lte: '<='
+        lte: '<=',
+        contains: 'contains'
       },
       operatorName: 'metadata_operator'
     })
@@ -307,7 +308,7 @@ class MetadataValueFilter extends Filter {
 
   deserialize (input, operator) {
     // Math comparison operators expect floats
-    if (operator === 'eq') return input
+    if (['eq', 'contains'].includes(operator)) return input
     const number = parseFloat(input)
     if (Number.isFinite(number)) return number
   }