Allow setting the destination branch/tag/ref so users can test the run
conditions based on the branch/tag/ref.
To simulate a pull request an user can define a ref that matches one of these
regular expressions: `refs/pull/(\d+)/head`, `refs/merge-requests/(\d+)/head`
Export clients and related packages.
The main rule is to not import internal packages from exported packages.
The gateway client and related types are totally decoupled from the gateway
service (not shared types between the client and the server).
Instead the configstore and the runservice client currently share many types
that are now exported (decoupling them will require that a lot of types must be
duplicated and the need of functions to convert between them, this will be done
in future when the APIs will be declared as stable).
The current config format was thought for future extensions for reusing runtimes
and job definitions adding some parameters.
After a lot of thoughts this looks like a complex approach: the final result
will be a sort of templating without a lot of powers.
Other approach like external templating should be an alternative but I really
don't think templating yaml is the way to go.
A much better approach will to just use jsonnet when we need to create matrix
runs and a lot of other use cases.
So just make the config a simple yaml/json. User can generate their config using
any preferred tool and in future we'll leverage jsonnet automated parsing and
provide a lot of jsonnet based examples for most use cases.
Main changes:
* Runs are now an array and not a map. The run name is in the Name field
* Tasks are now an array and not a map. The task name is in the Name field
* Use https://github.com/ghodss/yaml so we'll use json struct tags and unmarshall functions
