[jampukka]

Should fix #192. A single-page reference of the configuration keys read by the core modules and the reference webapp.

• docs/overview/configuration.md
  • Every key read by src/ and webapp-jakarta/, with default, whether it is required, and a short description, grouped as the config is: service, collections, properties and columns, databases
  • Describes what the code actually does, including the traps: an empty value is not always "unset", an unknown output format is silently skipped, the metadata path must be absolute
  • "Not read by the code" lists keys that appear in example files or older docs but that nothing reads
  • Community modules (src-community/: tiles, smile, esbulk) are not covered; their READMEs are the reference
  • PostGIS joins are marked experimental
• Keeping it current
  • CONTRIBUTING.md and the changelog say a PR that changes a key is expected to update the page

Few functional changes noticed when documenting this stuff:

• servers=a, b is now trimmed like every other list key; before, it failed startup with a NullPointerException (one line in HakunaConfigParser.readServers, with a test)
• The PostGIS source no longer reads collections.<id>.id.alias, geometry.alias and properties.<p>.alias. They were a not-working and unfinished idea (properties.<p>.alias made startup fail with a NullPointerException). The keys are now ignored; ColumnAlias is replaced by a plain set of column names, as in the GPKG source
• docker/cfg: the example configs no longer set collections.<id>.writeNulls and geometry.storageSrid, which nothing reads. addresses_view declares its storage SRID with srid.storage instead