Merge readExistingSerial and readExistingContent into a single
readExisting function to eliminate duplicate file I/O. Extract dateBase
helper to deduplicate serial formula between defaultSerial and
bumpSerial. Cache hash results during collision check to avoid
recomputing per member. Normalize error prefixes (remove "error:" from
fmt.Errorf, add uniformly at print sites). Use filepath.Join instead of
manual "/" concatenation. Replace trivial containsStr wrapper with
strings.Contains. Simplify tokenize to a single return. Use writeTestFile
and fixedTime helpers consistently in tests.
Generate RFC 9432 DNS catalog zone files from a declarative input file.
Parses zone-to-catalog assignments with optional group and coo properties,
produces deterministic BIND-format output with automatic SOA serial
management and change detection.
