Added ADR for Identity to move to TRS (#934)

docs/adr/0001-move-id-into-trs.md

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+# 1. Record architecture decisions
+
+Date: 2023-11-30
+
+## Status
+
+Accepted
+
+## Context
+
+With the adoption of Gov.OneLogin into our services, it renders a proportion of Teaching Identity's functionality either duplicated or obsolete. Therefore, we reviewed how best to enable our services to 
+integrate with Gov.OneLogin and also provide the necessary teaching record authorisation (that Teaching Identity currently provides). We chose to keep the OAUTH based journey that allows services to pass a set of PII data to be checked against the database of qualified teachers (soon to be Teaching Record System).
+
+## Decision
+
+* Keep OAUTH journey code to authorise access to teaching record
+* Move the code from Get an Identity into Teaching record system
+* Archive / stop updating the Get an Identity code base
+* Remove the uid (of teaching identity) from use within teaching services
+* Use the GOV.OneLogin uid to join identities across services
+
+
+## Consequences
+Register for a national qualification and claim teacher payments services will need to  make relatively mionor changes to their matching code.
+
+We will need to re-factor Teaching Record Sytem accordingly to provide teaching record authorisation via the OAUTH journey (copied from Get an Identity)
+
+Repos Affected:
+https://github.com/DFE-Digital/get-an-identity
+https://github.com/DFE-Digital/teaching-record-system
+