501 copy component fails when selecting a newer srg version and a control has been previously deleted in the source component

[vanessuniq]

Fixed bug #501
Refactored the logic of Component#duplicate and Component#from_mapping to correctly copy a component and update the rules based a given new srg:

• Fixed the incorrect use of ActiveRecord methods where & pluck:
  • where & pluck applies on the database level. So if the model instance the method is being called on is not persisted, the return value is an empty list. Switched to use enumerator methods select and map instead to get the expected behavior.
• Updated the based_on attribute of the new (copied) component to be the new given srg
• Fixed #from_mapping method to correctly check if a new list of rule versions was provided for import or if a null value was given
• Fixed how new Rule#rule_id are generated when importing new rules to always generate unique rule_id for a rule in a given component: rule_id was generated based on the (total count of rules + 1) of the component. This created an error due the uniqueness constraint of rule_id in a given component in the scenario when some rules have been deleted from the component. Fixed it to generate new rule_id based on the largest_rule_id in the given component.
  e.g. scenario:
  1. Take component with rules ['000001', '000002', '000003']
  2. Delete the rule with rule_id '000001' from the component
  3. Now the component has rules ['000002', '000003'] total count = 2
  4. Adding a new rule to the component:
     * Generating new rule_id based on total count + 1 will generate '000003' which already exist => causing db error
     * Generating new rule_id based on largest_rule_id + 1 will generate '000004'

[freddyfeelgood]

Looks good in our tests.