Handle `.agola/config.star` files in starlark config format.
To provide a context like done for jsonnet we require that the starlark agola
config file contains a main function that will receive a config context as a
dict.
We also had to implement our own json conversion from a starlark dict since go
starlark removed its own function.
During tests provide a zaptest Logger so all services output will be redirected
to golang testing logger.
When multiple services of the same type are provided add a unique name field to
distinguish them.
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).
Since they're not types common to all the services but belongs to the
configstore.
Next step will be to make them local to the configstore and not directly used by
other services since these types are also stored.
