This is the template in Documenting architecture decisions - Michael Nygard. You can use adr-tools for managing the ADR files.
In each ADR file, write these sections:
# Title
## Status
- What is the status (proposed, accepted, rejected, deprecated, superseded etc.)?
## Context
- What is the issue that is motivating this decision or change?
## Decision
- What is the change that we are proposing and/or implementing?
## Consequences
- What becomes easier or more difficult to do because of this change?