Refactor auth by adding GitHub Enterprise provider

[gkuga]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 20.94%. This pull request decreases coverage by -0.00%.

File	Function	Base	Head	Diff
pkg/oauth/github/github.go	newGHEOAuthClient	--	0.00%	+0.00%
pkg/model/project.go	ProjectSSOConfig.GenerateAuthCodeURL	0.00%	0.00%	+0.00%
pkg/model/project.go	ProjectSSOConfig_GitHub.GenerateAuthCodeURL	0.00%	0.00%	+0.00%
pkg/oauth/github/github.go	NewOAuthClient	0.00%	0.00%	+0.00%

[nghialv]

Thank you.
/approve

[pipecd-bot]

This pull request is APPROVED by nghialv.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.

[pipecd-bot]

failed to handle template rule examples

Details

Error: unabled to push rendered files to destination