[RFC-007] Flux cmd support for GitHub provider: This commit includes the following changes -

- Add flux create secret githubapp command that accepts and validates the inputs to create a github app secret with options to export the secret yaml or create the secret directly in the Kubernetes cluster

- Add tests for flux create secret githubapp command

- Add flux create source git command that accepts and validates the inputs to create a gitrepository source with for github provider with options to export the source yaml or create the github gitrepository source directly in the Kubernetes cluster.

- Add tests for flux create source git command for github provider.

Signed-off-by: Dipti Pai <diptipai89@outlook.com>

pkg/manifestgen/sourcesecret/options.go

@@ -75,6 +75,12 @@ type Options struct {
 	VerificationCrts    []VerificationCrt
 	TrustPolicy         []byte
 	Address             string
+
+	// GitHub App options
+	GitHubAppID             string
+	GitHubAppInstallationID string
+	GitHubAppPrivateKey     string
+	GitHubAppBaseURL        string
 }
 
 type VerificationCrt struct {