Added CompanyableTrait to Department model

[marcusmoore]

Description

This PR adds a couple (see edit) simple tests around the Api/DepartmentsController's index method to ensure it returns the number of rows expected (specific values aren't tested) and that the results adhere to full company scoping when it is enabled.

Since we have a passing test for adhering to company scoping we can add the CompanyableTrait to the Department model and remove the Company::scopeCompanyables() wrapper in the controller.

This is another small step in the direction of simplifying how models are scoped to companies.

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Edit: snuck in a couple more simple tests for authentication and authorization.

Type of change

• Bug fix (non-breaking change which fixes an issue) (sort of ❓)

[what-the-diff]

PR Summary

• Enhanced Data Selection in Department Details
  Upgraded the process of data retrieval for department details. Now, it focuses only on specific columns from the 'departments' table, reducing data load. Additionally, the image of each department is now part of the data selected, which should enhance the visual presentation. The number of users in each department is also counted and attached for reference, aiding in usage analytics.

• Incorporated CompanyableTrait in Department Model
  Introduced a new trait, 'CompanyableTrait,' into the department model. This trait signifies that our department can inherit certain functionalities related to the company context, providing greater flexibility and reusability of code.

• Added DepartmentIndex Tests
  Introduced new test cases to ensure that the 'Department Index' endpoint works correctly. It is now confirmed that 'DepartmentIndex' returns the expected departments and strictly adheres to company scoping, providing proof of reliability and adherence to business rules.

[marcusmoore]

@snipe is there anything holding this back?