---
- project_variables: variables = GET projects/:project_id/variables?
- project_variable: variable = GET projects/:project_id/variables/:variable_key
- create_project_variable: variable = POST projects/:project_id/variables?
- edit_project_variable: variable = PUT projects/:project_id/variables/:variable_key?
- delete_project_variable: DELETE projects/:project_id/variables/:variable_key
