Add a LessonPlan model
Add factory for LessonPlan model
Add spec for LessonPlan model and its class methods
Add validation for LessonPlan's name, description and plan
Store Resource index in lesson plan, rather than storing the whole resource
Save LessonPlan to neo4j if it's valid
Rename Resource model's field  into
Merge patch from model/resources (rename type column)
Change Resource's factories to use resource_type instead of type
Change Resource spec and Contains spec to make use of Resource's  instead of
Change Resource and ResourceValidator to make use of  instead of
Merge branch 'model/resource' into model/lesson_plan
Update spec for new design of LessonPlan#resources and LessonPlan#goals
Store type of the result used in each lesson plan's step
Add resource_count to LessonPlan factory
Add triat to create/build lesson plan without resouce_count in plan
LessonPlan.resources must return a non-empty array of existing Resources' info
LessonPlan without resource_count should not be valid
Define the resources method for LessonPlan
Validate presence of resource_count key in LessonPlan's plan