Introduce a notion of release into sfpowerscripts

[azlam-abdulsalam]

sfpowerscripts currently do not have a notion of 'release'. The new fetch command, existing deploy and changelog generator all need to be combined to form a notion of release. Most of this information then lives in the form of YAML file of the particular CI/CD platform. This inturn impacts the portability of sfpowerscripts and is also tied into the CI/CD platform.

sfpowerscripts will introduce a release command that utilises a release definition file (YAML format) and it will combine all the above commands to provide a notion of release

Features being proposed are

• Fetch artifacts based on the release definition
• Manage external dependency such as managed packages
• Preview changelog
• Display a list of metadata that is to be added / changed
• Option to dry run a release, to understand what artifacts go into a release
• Commit changelog to a particular branch

[azlam-abdulsalam]

An ADR has been created for this
https://github.com/Accenture/sfpowerscripts/blob/develop/ADR/release/release.md

[azlam-abdulsalam]

@aly76 will keep this open until changelog and dry run goes through.Or do you want to raise another issues?