MedEvac: dual-language email notifications

[morgang-adappt]

Description

Plumbs a language field through EmailNotification (model, GraphQL input, GraphQL type, and the add/edit mutations) so a notification can record which language its content should be resolved in. Also translates the medevac email-notification keys in uk.json.

Useful links

• Please insert link to ticket
• MedEvac: dual-language email notifications ems-frontend#2921
• Please insert any useful link ( documentation you used for example )

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

• Test A
• Test B

Screenshots

Please include screenshots of this change. If this issue is only back-end related, and does not involve any visual change of the platform, you can skip this part.

Checklist:

( * == Mandatory )

• * I have set myself as assignee of the pull request
• * My code follows the style guidelines of this project
• * Linting does not generate new warnings
• * I have performed a self-review of my own code
• * I have put the ticket for review, adding the oort-backend team to the list of reviewers
• * I have commented my code, particularly in hard-to-understand areas
• * I have put JSDoc comment in all required places
• * My changes generate no new warnings
• * I have included screenshots describing my changes if relevant
• * I have selected labels in the Pull Request, according to the changes with code brings
• I have made corresponding changes to the documentation ( if required )
• I have added tests that prove my fix is effective or that my feature works
• * New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules