MG-2147 - Generate mocks with mockery for Consumer service

[nyagamunene]

What type of PR is this?

This is a feature because its add the following functionality: generates mocks for consumers.

What does this do?

It generates the mocks for consumers service.

Which issue(s) does this PR fix/relate to?

• Related Issue Feature: Generate mocks with mockery for Consumers service #2147
• Resolves Feature: Generate mocks with mockery for Consumers service #2147

Have you included tests for your changes?

Yes, I have included tests

Did you document any new/modified feature?

No, I have not updated the documentation.

Notes

[dborovcanin]

Simplify and rename (and don't export):

func subscriptionsSlice(subs []sdk.Subscription, start, end int) []notifiers.Subscription {
	var res []notifiers.Subscription
	for i := start; i < end; i++ {
		sub := subs[i]
		res = append(res, notifiers.Subscription{
			ID:      sub.ID,
			OwnerID: sub.OwnerID,
			Contact: sub.Contact,
			Topic:   sub.Topic,
		})
	}
	return res
}

[dborovcanin]

User string instead of the full response; return response in the assert. Do the same for all the other test cases.