docs(adr): setup ADR process 0001 (runatlantis#3405)

.adr-dir

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+docs/adr

docs/adr/0001-record-architecture-decisions.md

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+# 1. Record architecture decisions
+
+Date: 2023-05-09
+
+## Status
+
+Accepted
+
+## Context
+
+We need to record the architectural decisions made for Atlantis. The project is a very decentralized project. It suffers from frequent one-timer contributors and an ever-changing team of maintainers.
+By utilizing the ADR process, we can improve who decisions are made and bring transparency to past decisions to assist future contributors and maintainers to confidently steer the project.
+
+## Decision
+
+We will use Architecture Decision Records, as [described by Michael Nygard](http://thinkrelevance.com/blog/2011/11/15/documenting-architecture-decisions).
+
+## Consequences
+
+See Michael Nygard's article, linked above. For a lightweight ADR toolset, see Nat Pryce's [adr-tools](https://github.com/npryce/adr-tools) before submitting a new ADR.