Add link to initiating PR in notification email to CLA manager

[brianwarner]

Summary

The notification email which is sent to a CLA manager contains the org for the CLA, but this is not enough to infer the specific contribution for which a signature is required.

In the notification email, can you please add a link to the PR which caused the notification? For example:

This is a notification email from EasyCLA regarding the organization Fidelity Investments.

The following contributor would like to submit a contribution to the projects(s): xxxxxx and is requesting to be added to the approval list as a contributor for your organization:

Pull request: https://github.com/xxx/xxx/pull/xxx

Name/User Name: xxxx, GitHub User Name: xxx, Emails: xxx@yyy.com

CLA Managers can visit the EasyCLA corporate console page...

Background

Provide context to the feature request - provide steps to indicate how this feature would be realized, such as:

1. CLA manager is sent an email which contains the signature request
2. CLA manager can click a link and go straight to the PR that triggered the request

User Story

• As a CLA manager, I want to know what contribution I'm approving when a new request comes in.

Acceptance Criteria

1. Link to the PR is included in the notification email

[lukaszgryglicki]

#5030

[lukaszgryglicki]

The above PR (#5030) merged, I will also create prod PR for this.

[lukaszgryglicki]

This feature will was merged into python -> golang porting PR: #5027 - this will be merged & deployed after the intercom release.

[lukaszgryglicki]

This is deployed to prod with #5027 (release https://github.com/linuxfoundation/easycla/releases/tag/v2.6.0).