Allow School Administrators to invite users via School Dashboard in Manage School Experience

[ekumachidi]

Trello card

#5535

Context

We know that users have often had difficulty getting access to Get School Experience. Because of a 2 stage auth process that they have to do in order to get initial access to GSE.

• Firstly, they had to request linkage to a school

• Secondly, they had to request the ‘role’ for get school experience

We want to enable school administrators to invite users to the school that they administer through 'School Dashboard'

Changes proposed in this pull request

• Updates preliminary copy on the GSE app
• Add users resource to routes.rb
• Adds links to manage users on the school dashboard
• Adds UsersController
• Adds views to manage users in a school
• Adds DSI API service to fetch school's ukprn from DSI
• Adds DSI API service to fetch users in a school
• Adds DSI API service to add users to a school
• Adds relevant specs

[MylesJarvis]

We also need to remove these two links from Help and Support. I think Tejas covered this before moving over to TRA but adding here for completeness.

[github-actions[bot]]

Review app deployed to https://get-school-experience-review-pr-3102.test.teacherservices.cloud :white_check_mark: DfE sign in route obtained: https://get-school-experience-review-pr-1.test.teacherservices.cloud