Resolve "Update docs for v1.12.3"

Description

Update release notes for v1.12.3

Related issues/MRs

#260 (closed). Relevant for !494 (merged), !501 (merged), !502 (merged)

Notes to review

Merge checklist

• Self-review of code performed
• Changes has been reviewed by other core developer. Apply label: code reviewdone

Closes #260 (closed)