History of Credentials::fmt 1 change

In crates/oxy-strata/src/lib.rs, lines 216–224 on v0.4.6. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 216,224:crates/oxy-strata/src/lib.rs.