Implement Uri Provider for the Api-Gateways

## Description
The current implementation has the URI for the gateways tied to the local server of the application. We need to abstract the implementation and create a provider that will give the gateways the valid connection string.

## Acceptance Criteria

- Can work with local and non-local servers
- Will find and provide the correct host URL
- Proper error handling and presentation is included

## Implementation
- Firstly investigate whether we can get the host url and whether it is a valid approach
- Create a ServerUrlProvider
- Create a Horizons gateway Uri provider. Refactoring the current uri construction away from the gateway
- Register the service