FerretDB document defaults, PostgreSQL default URL, disable telemetry

[minijackson]

Description of changes

• Move the default settings into options, so that they are documented in the options list
• set a default value for the PostgreSQL URL, to provide a nice default if the end user wants to use the PostgreSQL backend
• Disable telemetry by default

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

cc @JulienMalka @camillemndn

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[minijackson]

Friendly ping: @JulienMalka @camillemndn

[AlekSi]

FerretDB developer there. Why disable telemetry by default?

[minijackson]

@AlekSi hey! It's kind of an unwritten rule inside of nixpkgs to disable telemetry by default. Some of our users expect it.

[JulienMalka]

Running the sqlite test, I get:
The option nodes.machine.services.ferretdb.settings' is used but not defined.`

[minijackson]

@JulienMalka done, thanks!