Add std.trim for string (#1067)

* Add std.trim for string

Author: Tejesh-Raut

doc/_stdlib_gen/stdlib-content.jsonnet

@@ -371,6 +371,14 @@ local html = import 'html.libsonnet';
             Returns true if the the given string is of zero length.
           |||,
         },
+        {
+          name: 'trim',
+          params: ['str'],
+          availableSince: 'upcoming',
+          description: |||
+            Returns a copy of string after eliminating leading and trailing whitespaces.
+          |||,
+        },
         {
           name: 'equalsIgnoreCase',
           params: ['str1', 'str2'],

stdlib/std.jsonnet

@@ -1759,4 +1759,6 @@ limitations under the License.
     for k in std.objectFields(obj)
     if k != key
   },
+
+  trim(str):: std.stripChars(str, ' \t\n\f\r\u0085\u00A0'),
 }

test_suite/stdlib.jsonnet

@@ -1575,4 +1575,10 @@ std.assertEqual(std.removeAt([1, 2, 3], 1), [1, 3]) &&
 
 std.assertEqual(std.objectRemoveKey({ foo: 1, bar: 2, baz: 3 }, 'foo'), { bar: 2, baz: 3 }) &&
 
+std.assertEqual(std.trim('already trimmed string'), 'already trimmed string') &&
+std.assertEqual(std.trim('    string with spaces on both ends     '), 'string with spaces on both ends') &&
+std.assertEqual(std.trim('string with newline character at end\n'), 'string with newline character at end') &&
+std.assertEqual(std.trim('string with tabs at end\t\t'), 'string with tabs at end') &&
+std.assertEqual(std.trim('string with other special whitespaces at end\f\r\u0085\u00A0'), 'string with carriage return at end') &&
+
 true