create service for line_extension
create validator for line_extension associate
implement association in line_extension DAO
implement association in line_extension notifier
fix pep8 warnings and spelling errors
implement line_extension.get_by_line_id
add exceptions for line_extension dao
refactor validation tests, split into smaller units
refactor dao tests, regroup common prerequisites
refactor validator, use line_extension dao instead of ULE
add find_by_extension_id to line_extension dao
implement dissociation in line_extension service
implement dissociation validation for line_extension
implement dissociation in dao for line_extension
rename private methods to make code more clear
implement dissociation in line_extension notifier
remove user_line if no longer associated to nothing
update user_line when created with an extension
add dao method to extension service
make sure dao returns a line_extension model