Do we need the full flexibility of install.yaml?

[negz]

Currently the packages design includes an install.yaml, which determines how the packaged controller is spun up. This was designed for a more open ended take on packages, in which a package could include any kind of Kubernetes controller.

Now that we're only ever packaging provider controllers we might reconsider this level of flexibility per https://github.com/crossplane/crossplane/issues/1441. We should likely not change anything for our scoped-september branch, but we may want to consider what our 'north star' take on this is.

[negz]

CC @lukeweber - raised this to followup on what we're doing with install.yaml.

[hasheddan]

A few notes and related issues here:

• There are two main parties who may want to configure the a provider package's controller: package author and package consumer. The package author may need to configure part of the Deployment, such as the SecurityContext to support certain required functionality. A package consumer may want to configure something like the resource requests and limits for the package.
• The current install.yaml exposes all of the configurable options of a Deployment, which is useful because it doesn't require constantly changing our own API to support different options. However, the install.yaml may be modified by the current package manager if it contains prohibited fields (i.e. allowPrivilegeEscalation: true), which can be confusing and opaque for a package author.
• The current install.yaml may have some fields overwritten by configuration on a ClusterPackageInstall at install time, such as imagePullSecrets, which can also be unexpected for a package author.
• One option could be to allow the package author to define a full Deployment, then allow a user to patch it as they see fit (optionally overwriting things like image, which would fundamentally change the package) via the package installation process.
• The package manager could accept configuration at runtime which dictates automatic modifications that will be made to package Deployments.
• NodeSelector on ClusterPackageInstaller
• Env var support for packages to enable users to supply proxy credentials
• Support Packaged controller configuration