Added create organisation endpoint and service layer

[EmmaFuller437]

URP-123 - Short Description

Summary

This ticket is for implementing this feature.

Screenshots / Evidence

Screenshots of the feature if applicable

Risks and follow-up

• There is a TODO here as we are awaiting a dependent piece of functionality.
• I was unsure the best way to write this function, please pay extra attention to it during review

Checklist

• Tests added or updated where appropriate
• Linting and formatting pass
• Accessibility considered for UI changes
• Security/privacy impact considered
• Documentation updated where needed