Fix tags search and hint while adding tags to test cases in TP

How to reproduce:
- Open a Test Plan
- Go to Cases tab
- Select few test cases
- click Tag -> Add Tag button
- start typing tag name
- if there are tags which match the text they will be shown
  as a drop-down hint. This was previously raising an exception.

Also introduced a slight performance optimization by using
QuerySet.values() method to fetch only the field name we're interested
in, not everything.

Note: this commit makes use of the TestCaseTag class instead of the
TestTag class in order to convert ORM queries to child -> parent
relationship, instead of parent -> child one.

Updated JavaScript files to match the backend changes and model
field names.

Note:
Removal of tags bug is Nitrate#174 which is fixed in PR Nitrate#177

Signed-off-by: Mr. Senko <atodorov@mrsenko.com>

tcms/core/ajax.py

@@ -23,7 +23,7 @@
 from tcms.management.models import Component, TestBuild, Version
 from tcms.management.models import Priority
 from tcms.management.models import TestTag
-from tcms.testcases.models import TestCase, TestCaseBug
+from tcms.testcases.models import TestCase, TestCaseBug, TestCaseTag
 from tcms.testcases.models import TestCaseCategory
 from tcms.testcases.models import TestCaseStatus
 from tcms.testcases.views import get_selected_testcases
@@ -121,13 +121,13 @@ def env_values(self):
 
         def tags(self):
             query = strip_parameters(request, self.internal_parameters)
-            tags = TestTag.objects
+            tags = TestCaseTag.objects
             # Generate the string combination, because we are using
             # case sensitive table
             if query.get('name__startswith'):
                 seq = get_string_combinations(query['name__startswith'])
                 tags = tags.filter(eval(
-                    '|'.join(["Q(name__startswith = '%s')" % item for item in seq])
+                    '|'.join(["models.Q(tag__name__startswith = '%s')" % item for item in seq])
                 ))
                 del query['name__startswith']
 
@@ -145,15 +145,15 @@ def versions(self):
 
             return Version.objects.filter(product__id=self.product_id)
 
-    objects = Objects(request=request, product_id=request.GET['product_id'])
+    objects = Objects(request=request, product_id=request.GET.get('product_id'))
     obj = getattr(objects, request.GET['info_type'], None)
 
     if obj:
         if request.GET.get('format') == 'ulli':
             field = request.GET.get('field', 'name')
             response_str = '<ul>'
-            for o in obj():
-                response_str += '<li>' + getattr(o, field, None) + '</li>'
+            for o in obj().values(field):
+                response_str += '<li>' + o.get(field, None) + '</li>'
             response_str += '</ul>'
             return HttpResponse(response_str)
 

tcms/static/js/testplan_actions.js

@@ -2468,8 +2468,8 @@ function constructBatchTagProcessDialog(plan_id) {
           'name__startswith': request.term,
           'info_type': 'tags',
           'format': 'ulli',
-          'testcase__plan__pk': plan_id,
-          'field': 'name'
+          'case__plan': plan_id,
+          'field': 'tag__name'
         },
         'success': function(data) {
           var processedData = [];