add model for provenance

smash/web/models/provenance.py

+# coding=utf-8
+from django.db import models
+
+
+class Provenance(models.Model):
+    class Meta:
+        app_label = 'web'
+
+
+    modified_table = models.CharField(max_length=1024,
+                                     verbose_name='Modified table',
+                                     blank=False, null=False
+                                    )
+
+    modified_table_id = models.CharField(max_length=1024,
+                                     verbose_name='Modified table row',
+                                     blank=False, null=False
+                                    )
+
+    modification_date = models.DateTimeField(
+        verbose_name='Modified on',
+        null=False, blank=False,
+        auto_now_add=True
+    )
+
+    modification_author = models.ForeignKey("web.Worker",
+                            verbose_name='Worker who modified the row',
+                            null=True, blank=False
+                        )
+
+    modified_field = models.CharField(max_length=1024,
+                                     verbose_name='Modified field',
+                                     blank='', null=False
+                                    )
+
+    previous_value = models.CharField(max_length=2048,
+                                      verbose_name='Previous Value',
+                                      blank=True, null=True)
+
+    new_value = models.CharField(max_length=2048,
+                                      verbose_name='New Value',
+                                      blank=True, null=True)    
+
+    modification_description = models.CharField(max_length=20480,
+                                     verbose_name='Description',
+                                     blank=False, null=False
+                                    )
\ No newline at end of file