Add CHANGELOG entries for v0.3.1 and v0.3.2 #387

Job	Run time
Test Suite (default)	1m 10s
Test Suite (protobuf)	1m 11s
Test Coverage	8m 47s
Check	1m 6s
Check license and vulnerabilities	1m 56s
Clippy	1m 6s
ETSI	56s
Rustfmt	7s
Test Suite (all)	2m 9s
Test Suite (async-psql)	1m 39s
Test Suite (psql)	2m 3s
	22m 10s

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