Extend DORA4 API support for a specific environment name

Release notes

As a user with multiple production environments, I want to be able to see the metric(s) for a specific environment and not necessarily the entire group of production environments. In this issue we are adding the ability to specify a specific environment to retrieve metrics from.

Problem to solve

Coming from #296849 (comment 546261345)

As a user with multiple production environments, I want to be able to see the metric(s) for a specific environment and not necessarily the entire group of production environments.

Proposal

Add environment_name as an optional attribute to the get DORA4 API.

Get project-level DORA metrics.

GET /projects/:id/dora/metrics

Attribute	Type	Required	Description
id	integer/string	yes	The ID or URL-encoded path of the project can be accessed by the authenticated user.
metric	string	yes	The metric name. One of deployment_frequency or lead_time_for_changes.
start_date	string	no	Date range to start from. ISO 8601 Date format, for example 2021-03-01. Default is 3 months ago.
end_date	string	no	Date range to end at. ISO 8601 Date format, for example 2021-03-01. Default is the current date.
interval	string	no	The bucketing interval. One of all, monthly or daily. Default is daily.
environment_tier	string	no	The tier of the environment. Default is production.
environment_name	string	no	The name of the environment. Default is production.

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