Various minor improvements

[b4l]

• I agree to follow the project's code of conduct.
• I added an entry to the project's change log file if knowledge of this change could be valuable to users.
  • Usually called CHANGES.md or CHANGELOG.md
  • Prefix changelog entries for breaking changes with "BREAKING: "

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• Set default item type of collection as feature.
• Define numeric feature id as u64.
• Remove default Crs implementation.
• Skip serializing empty query parameters.
• Allow unbound feature pagination.