feat: adding Opsgenie plugin DOCS (#649)

* feat: adding Opsgenie plugin DOCS

* adding Opsgenie to SupportedDataSources.md

* Fixed typo

* fix: checkout main file versioned_docs/version-v0.19/Overview/SupportedDataSources.md

docs/Configuration/Opsgenie.md

@@ -0,0 +1,83 @@
+---
+title: "Opsgenie"
+sidebar_position: 11
+description: Config UI instruction for Opsgenie
+---
+
+Visit Config UI at: `http://localhost:4000`.
+
+## Step 1 - Add Data Connections
+
+On the Connections page, you can select Opsgenie and create a new connection on it.
+
+### Step 1.1 - Authentication
+![opsgenie-add-data-connections](images/opsgenie-create-a-connection.png)
+
+#### Connection Name
+
+Give your connection a unique name to help you identify it in the future.
+
+#### Endpoint URL
+
+Opsgenie makes available two types of REST API endpoints, US and EU, eg. `https://api.opsgenie.com/` or `https://api.eu.opsgenie.com/`. You can choose wich instance by selecting the due radio input.
+
+#### API Access Key
+
+In the `API key management` section of your Atlassian Opsgenie account settings, you can create a API key to manage your requests.
+
+Learn about [how to create a Opsgenie API key](https://support.atlassian.com/opsgenie/docs/api-key-management/). The following permissions are required to collect data from repositories:
+
+- `Read`
+- `Create and Update`
+- `Configuration Access`
+
+#### Proxy URL (Optional)
+
+If you are behind a corporate firewall or VPN you may need to utilize a proxy server. Enter a valid proxy server address on your network, e.g. `http://your-proxy-server.com:1080`
+
+#### Fixed Rate Limit (Optional)
+
+DevLake uses a dynamic rate limit to collect Opsgenie data. You can adjust the rate limit if you want to increase or lower the speed.
+
+Opsgenie doesn't establishes a maximum rate limit for its API request, thus you should check this **[detailed doc](https://docs.opsgenie.com/docs/api-rate-limiting)** on how to calculate your rate limit, based on number of user and account plan that you hired. For now, the default rate limit is in 6,000 request/hour (100 request/minute).
+
+#### Test and Save Connection
+
+Click `Test Connection`, if the connection is successful, click `Save Connection` to add the connection.
+
+### Step 1.2 - Add Data Scopes
+
+#### Services
+
+Choose the Opsgenie services you wish to collect either by finding them in the miller column, or searching.
+
+![opsgenie-set-data-scope](images/opsgenie-add-data-scopes.png)
+
+## Step 2 - Collect Data in a Project
+### Step 2.1 - Create a Project
+Collecing Opsgenie data requires creating a project first. You can visit the Project page from the side menu and create a new project by following the instructions on the user interface.
+
+![create-a-project](images/create-a-project.png)
+
+### Step 2.2 - Add a Opsgenie Connection
+You can add a previously configured Opsgenie connection to the project and select the boards for which you wish to collect the data for.
+Please note: if you don't see the services you are looking for, please check if you have added them to the connection first.
+
+![add-a-connection](images/add-a-connection-project.png)
+
+### Step 2.3 - Set the Sync Policy
+There are three settings for Sync Policy:
+- Data Time Range: You can select the time range of the data you wish to collect. The default is set to the past six months.
+- Sync Frequency: You can choose how often you would like to sync your data in this step by selecting a sync frequency option or enter a cron code to specify your prefered schedule.
+- Skip Failed Tasks: sometime a few tasks may fail in a long pipeline; you can choose to skip them to avoid spending more time in running the pipeline all over again.
+
+![sync-policy](images/sync-policy.png)
+
+### Step 2.4 - Start Data Collection
+Click on "Collect Data" to start collecting data for the whole project. You can check the status in the Status tab on the same page.
+![collect-data](images/collect-data.png)
+
+
+## Troubleshooting
+
+If you run into any problem, please check the [Troubleshooting](/Troubleshooting/Configuration.md) or [create an issue](https://github.com/apache/incubator-devlake/issues)