feat: JournalDb trait #84

Job	Run time
rust-library-base / Feature Checks	3m 55s
rust-library-base / Base Checks / Test Suite	5m 14s
rust-library-base / Base Checks / doctest	6m 4s
rust-library-base / Base Checks / Rustfmt	36s
rust-library-base / Base Checks / Clippy	3m 24s
rust-library-base / Base Checks / Docs	2m 43s
	21m 56s

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