r311 0.4.3

• API list upkeep
  • Added: Espoo, Oulu (#2)
  • Changed: Turku (#2)
  • Deprecated: Ottawa, Siegburg, Northfield, Annaberg-Buchholz
• Introduced deprecation system of available APIs
  • Added a key "questioned" to the API list which signals that an API might be abandoned
  • Added a key "deprecated" to the API list which signals that an API is no longer functional
  • o311_api() now warns when an API is questioned
  • o311_api() now aborts when an API is deprecated
• Added pretty formatting of error messages
• Changed heuristics in o311_request_all() to compare requests using set equality of request IDs instead of exact object equality
• Fix bug where formal checks in validate_endpoints() create an invalid dataframe
• Ensure that API error handling always yields a valid condition object
• o311_api does not match regular expressions anymore
• o311_ok(error = TRUE) now returns an error instead of an error object
• Add an explanatory note if an HTTP error is unknown
• Added a CITATION file (#3)
• Added a codemeta file
• Add precomputed vignettes