Hyphens in RelationContext.name unsupported

[Michał Sawicz]

It's customary to include hyphens/dashes in relation names, but that means the context for a template in ServiceManager ends up as:

> {
> 'relation-name': {
> 'key': 'value',
> ...
> }
> }

This, then, means that in the template you'd want to go:

> {{ relation-name['key'] }}

But that won't work, because it's trying to subtract name from relation.

One approach would be to put all the relation contexts under a common key, changing the template to, for example:

> {{ ctx['relation-name']['key'] }}

Another would be to sanitize the relation names, or maybe an optional RelationContext.alias that would be used in the context?