openbangla-keyboard: 2.0.0 -> unstable-2023-07-21; add fcitx5 support

[eclairevoyant]

Description of changes

• 2.0.0 -> unstable-2023-07-21
  • needed for fcitx5 support
• fix meta
  • remove use of with lib; (see Tracking issue: remove overuses of with lib; #208242)
  • add self to maintainers
• fix IME support (ibus, fcitx5)
• remove existing package in favour of the IME-specific ones
  • Removed openbangla-keyboard from top-level, added throws alias for that
  • Added two new packages (ibus-engines.openbangla-keyboard and fcitx5-openbangla-keyboard)

I see there's a discrepancy with how ibus and fcitx5 handle their packages, but I didn't want to create a pattern that's never been seen before in nixpkgs.

Closes #182388

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• 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/)
• 23.11 Release Notes (or backporting 23.05 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.

[hqurve]

Perhaps the openbangla-keyboard derivation should be deprecated (placed in aliases.nix with a message suggesting ibus-engines.openbangla-keyboard and fcitx5-openbangla-keyboard) since the build fails with

 > CMake Error at CMakeLists.txt:79 (message):
>   Please set atleast ENABLE_IBUS or ENABLE_FCITX to be ON to build a backend

Besides that, both of ibus-engines.openbangla-keyboard and fcitx5-openbangla-keyboard build.

[eclairevoyant]

Thanks, I completely blanked on the package deprecation process. I'll take a look at that

[eclairevoyant]

I've removed the existing attribute, thanks for the suggestion!

[hqurve]

I tested the ibus engine and it works

[asifakonjee]

@eclairevoyant... fcitx5 will not work with OpenBangla Keyboard 2.0. It will work with OpenBangla Keyboard built from the develop branch of OpenBangla Keyboard's github repository till now.