docs: update ADR template (#7789)

* Update ADR template

The reason for this proposed update to the ADR template is twofold:

1. There's currently no easy way to cross-reference between ADRs and
   issues/PRs on GitHub. This may be easy to manage for those with
   context while they're working on implementing an ADR, but after time
   passes and for complex ADRs it gets more difficult for newcomers to
   the codebase to track both the implementation status of the ADR or
   its historical context and discussions.
2. We should not allow for "proposed" ADRs. An ADR is a **decision
   record**, which implies acceptance, and not a proposal. RFCs provide
   a mechanism to make proposals.

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Add example of one ADR superseding another

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Move "Proposed" ToC entries to "Accepted".

It's possible some of these should actually be "Implemented", but I did not try
to go through each one to distinguish.

* Revert "Move "Proposed" ToC entries to "Accepted"."

This reverts commit d8d2907e98.

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Fix Markdown formatting

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Add "Deprecated" section to ADR TOC

Signed-off-by: Thane Thomson <connect@thanethomson.com>

* Expand ADR template to explicitly cater for rejected ADRs

Signed-off-by: Thane Thomson <connect@thanethomson.com>

Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

docs/architecture/README.md

@@ -86,13 +86,16 @@ Note the context/background should be written in the present tense.
 - [ADR-075: RPC Event Subscription Interface](./adr-075-rpc-subscription.md)
 - [ADR-076: Combine Spec and Tendermint Repositories](./adr-076-combine-spec-repo.md)
 
+### Deprecated
+
+None
+
 ### Rejected
 
 - [ADR-023: ABCI-Propose-tx](./adr-023-ABCI-propose-tx.md)
 - [ADR-029: Check-Tx-Consensus](./adr-029-check-tx-consensus.md)
 - [ADR-058: Event-Hashing](./adr-058-event-hashing.md)
 
-
 ### Proposed
 
 - [ADR-007: Trust-Metric-Usage](./adr-007-trust-metric-usage.md)

docs/architecture/adr-template.md

@@ -6,12 +6,30 @@
 
 ## Status
 
-> A decision may be "proposed" if it hasn't been agreed upon yet, or "accepted"
-> once it is agreed upon. Once the ADR has been implemented mark the ADR as
-> "implemented". If a later ADR changes or reverses a decision, it may be marked
-> as "deprecated" or "superseded" with a reference to its replacement.
+> An architecture decision is considered "proposed" when a PR containing the ADR
+> is submitted. When merged, an ADR must have a status associated with it, which
+> must be one of: "Accepted", "Rejected", "Deprecated" or "Superseded".
+>
+> An accepted ADR's implementation status must be tracked via a tracking issue,
+> milestone or project board (only one of these is necessary). For example:
+>
+>     Accepted
+>
+>     [Tracking issue](https://github.com/tendermint/tendermint/issues/123)
+>     [Milestone](https://github.com/tendermint/tendermint/milestones/123)
+>     [Project board](https://github.com/orgs/tendermint/projects/123)
+>
+> Rejected ADRs are captured as a record of recommendations that we specifically
+> do not (and possibly never) want to implement. The ADR itself must, for
+> posterity, include reasoning as to why it was rejected.
+>
+> If an ADR is deprecated, simply write "Deprecated" in this section. If an ADR
+> is superseded by one or more other ADRs, provide local a reference to those
+> ADRs, e.g.:
+>
+>     Superseded by [ADR 123](./adr-123.md)
 
-{Deprecated|Declined|Accepted|Implemented}
+Accepted | Rejected | Deprecated | Superseded by
 
 ## Context