Update Github Action pipeline documentation (#59)

* Update Github Action pipeline documentation

* Update TODO

dev_guides/github_action_pipeline.md

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+# Pipeline
+
+The EPIC project has moved away from PR based pipeline due to the complexity and reliability concerns of the PR based pipeline imlementation. The current CI/CD pipeline utilises Github Actions to build Docker images and push them back into the BC Gov OpenShift Docker registry.
+
+**TEST** and **PROD** environment promotions are also handled by Github Actions when automatically created promotion Pull Requests are merged into `promotion/test` and `promotion/prod` branches.
+
+## Requirements
+
+- OpenShift Service Account with `read` and `update` permission on OpenShift `imagestreams`, `imagestreamtags` and `imagetags`
+- Rocket.Chat webhook URL for deployment notifications
+
+### Github Secrets
+
+| Secret                        | Description                                                                                                                                    |
+| ----------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
+| OPENSHIFT_REPOSITORY          | OpenShift Docker repository URL                                                                                                                |
+| OPENSHIFT_REPOSITORY_USERNAME | OpenShift Docker repository login name, default is `serviceaccount`                                                                            |
+| OPENSHIFT_REPOSITORY_PASSWORD | OpenShift Docker repository password, can be found on the service account `dockercfg` secret                                                   |
+| OPENSHIFT_TOKEN               | OpenShift login token, can be found on the service account `token` secret                                                                      |
+| OPENSHIFT_URL                 | OpenShift platform URL, same as the one in the `oc login` command                                                                              |
+| PERSONAL_ACCESS_TOKEN         | Github Personal Access Token for `epicbcdk` account with `repo` permissions. This is needed to allow Github Actions to trigger other workflows |
+| ROCKET_CHAT_URL               | Rocket.Chat webhook URL for deployment notifications                                                                                           |
+
+## GitHub Branches
+
+EPIC's active default branch is the **develop** branch, developers should branch from and make pull requests to it. **main** branch contains the code that is active in production.
+
+- **develop** - default branch, all pull requests branch from it
+- **test** - CI branch, keep record of code deployed in TEST
+- **main** - CI branch, keep record of code deployed in PROD
+
+## Pipeline Flow
+
+A fix or feature may require pull requests to a subset of eagle api, public, and admin repositories.
+
+Test and Prod environment promotions are done using the automatically created pull requests against the `promotion/test` and `promotion/prod` branches. The `promotion/test` and `promotion/prod` branches are simplied used to track currently deployed commit hashes in the TEST and PROD environments. They are also used to trigger the deployment Github Action workflows.
+
+1. Create a pull request to one of the eagle repositories
+2. SonarCloud scan and Github Action unit tests and linting run
+3. Trigger builds upon dev pull request merge
+4. `:ci-latest` image is built and pushed into OpenShift repository
+5. **TEST** promotion pull request is automcatically created against `promotion/test` branch
+6. Trigger **TEST** deployment when `promotion/test` pull request is merged
+7. **PROD** promotion pull request is automcatically created against `promotion/prod` branch
+8. Trigger **PROD** deployment when `promotion/prod` pull request is merged
+
+![Pipeline](images/eagle-pipeline-2021.jpg)
+
+## TODO
+
+- Re-implement the **hotfix** branch pipeline
+- Re-implement the PR based pipeline with better reliability 

dev_guides/pull_request_pipeline.md

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+# Deprecated
+EPIC projects no longer uses the PR based pipeline due to complexity and reliability concerns of its implmentations.
+
+The project has switched to using a Github Action based pipeline [documented here](github_action_pipeline.md).
+
+
 # PR Based Pipeline
 
 Eagle projects are built using a Pull Request based pipeline and CI/CD flow using Jenkins.