* Add support for custom metrics for HPA
* Cleanup TargetCPUPercent references from possible places
* HPA v2beta has 80% default cpu limit if not set
Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
This PR adds an interface for controller API client, it allows us to
implement mock API client for unit testing with ease and we are
able to generate spec file without accessing the real Fission server.
Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse
the functions nor writing unit tests. This PR aims to make functions
return errors instead of error out.
