Provide an API for accessing BoundedContexts and Domains

[Nagelfar]

In some situation you want to use data gathered in Contexture in 3rd party tools.

E.g. you want to verify & apply names of domains / bounded contexts to 'labels' of tools. (E.g. in monitoring tools attach a label named after the bounded-context to the log. In Kubernetes name a namespace after a domain;)

Potential API endpoints:

• all domains
• all bounded contexts
• all subdomains / bounded contexts of one domain

[Nagelfar]

Currently an backend API exists with these main entry points and sub-routes (currently only documented as part of the routing configuration):

• api/domains for accessing domains
• api/boundedContexts exposes bounded contexts and provides a basic search functionality (currently documented by these tests)
• api/collaborations exposes the collaborations between bounded contexts or domains
• api/namespaces/templates exposes the defined templates for namespaces

These endpoints could be extended into a more REST-full API containing REL-links and possible actions for resources.