Allow endpoint details to influence the output

A service-target is currently returning a `[]string` to model endpoints.
Let this to be a struct `[]Endpoint` where more than strings can be defined.

This will allow the Endpoint writer to enhance the look of the endpoints when needed.
For example, from something like

```
(✓) Done: Deploying service api
- Endpoint: https://api-erixlchzvcltg.azurewebsites.net/
- Endpoint: https://api-erixlchzvcltg-staging.azurewebsites.net/
- Endpoint: https://api-erixlchzvcltg-test.azurewebsites.net/
```

to:

```
(✓) Done: Deploying service api
- Main App: https://api-erixlchzvcltg.azurewebsites.net/
- Slot foo: https://api-erixlchzvcltg-staging.azurewebsites.net/
- Slot bar: https://api-erixlchzvcltg-test.azurewebsites.net/
```