GraphQL query for fetching deployment information

Problem

environments.json endpoint is getting bloated and becoming one of the heavy and fragile endpoint. We should split it for each purpose.

Proposal

Add the following GraphQL queries:

• Deployment Lists
  • Returns DeploymentType GraphQL entity
  • Description: It returns the high-level overview of deployments of a specific environment.
  • Usage example: Deployment Index page (a.k.a. Environment Detail page)
  • Usage example: Update GraphQL API to support environment detail page
• Deployment Details
  • Returns DeploymentDetailsType GraphQL entity
  • Description: It returns the details of a specific deployment.
  • Usage example: Show tags related to deployed commit on Environment Page
  • Usage example: Show tags related to deployed commit on Environment Detail Page
  • Usage example: Deployment Issue (Deployment detail page)

Related

• https://docs.gitlab.com/ee/development/api_graphql_styleguide.html