refactor: make observation messages pure #2647

Job	Run time
Test memory (Nix)	3m 31s
Loadtest (Nix)	9m 37s
Lint & check code style	1m 31s
Test (Nix)	5m 56s
Test PG 9.6 (Nix)	4m 43s
Build Linux (Cabal, GHC 9.4.8)	2m 38s
Build Linux (Cabal, GHC 9.6.4)	1m 30s
Test PG 10 (Nix)	4m 52s
Build MacOS (Nix)	10m 51s
Build Linux (Cabal, GHC 9.8.1)	1m 30s
Test PG 11 (Nix)	4m 39s
Test PG 12 (Nix)	4m 34s
Test PG 13 (Nix)	4m 34s
Build Linux (Stack)	2m 50s
Build Linux static (Nix)	2m 27s
Test PG 14 (Nix)	4m 38s
Build MacOS (Stack)	3m 29s
Get FreeBSD build from CirrusCI	6m 17s
Test PG 15 (Nix)	4m 36s
Build Windows (Stack)	5m 50s
Test PG 16 (Nix)	4m 38s
Build aarch64 (Cabal, GHC 9.4.8)	0s
Prepare release	0s
Release on GitHub	0s
Release on Docker Hub	0s
Release Arm Builds on Docker Hub	0s
Remove copied files from server	0s
	1h 35m 11s

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