This PR introduces extensibility to the Fission CLI. The principle behind the design of this extensibility is taken from the approach git uses: the main binary (fission) calls other binaries (fission-workflows) - which it discovers using simple prefix-rules - based on specific commands (fission workflow <command>).
Environment Specs so far had only an image URL to specify a container image.
This was fine for public images but fell short in a few of cases:
(a) Using private image registries
(b) Specifying environment variables (this is needed for workflows helm install)
(c) Setting a SecurityContext for the container
This change adds the Container object to both build and runtime Environments.
Compatibility is preserved -- the existing ImageURL field is still used. See the comments in types.go for the overriding rules in the case that both Container and ImageURL are specified.
Create a container image with the buidler, so we can avoid copying the builder binary into the env container during the env container build.
Gather both stdout and stderr of a build into the logs.
* Add Dockerfile for builder + update release scripts
* Improve logging of buildermgr and builder
* Add support for environment-scoped buildcmd
* Fix fork/exec wd when package is a file
* Update tests to also include builder image
* Add logging to builder's fork/exec
Add a flag to the environment to control multiple specialization -- the max number of functions per container. This can be set to 1 or infinity.
Add an api proxy to workflow apiserver from the controller.
Add function metadata to FunctionLoadRequest; every v2 environment now knows which function it's loading (but can ignore that information if it wants to).
Add function identity headers to router. This is useful for multiple specialization, so the router can disambiguate between different function calls. (If this turns out to be a non-trivial perf overhead, we could add these headers conditionally, but for now they are always added.)
