Implement the geoip context

[Dakostu]

This change implements the geoip context - a built-in that reads MaxMind DB files and uses IP values in events to enrich them with the MaxMind DB geolocation data.

[tobim]

The diff here should hopefully fix the static binary build:

diff --git a/nix/overlay.nix b/nix/overlay.nix
index e3c04f88be..71f1e92e81 100644
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -168,6 +168,9 @@ in {
     prev.writeShellScriptBin name ''
       echo "stub-${name}: $@" >&2
     '';
+  libmaxminddb = overrideAttrsIf isStatic prev.libmaxminddb (orig: {
+    nativeBuildInputs = (orig.nativeBuildInputs or []) ++ [prev.buildPackages.cmake];
+  });
   fluent-bit = let
     fluent-bit' =
       overrideAttrsIf isDarwin prev.fluent-bit

[tobim]

This is already looking pretty good. I did not look at the conversion cases in detail, for those we need a functional test that hits all of the code paths.

[tobim]

I missed that we already have tests in the private repo.

[dominiklohmann]

This works well in practice; mostly questions now to get the UX right.

[dominiklohmann]

I think this is ready to be shipped. You likely need to rebase the context plugin changes after my blocking operators PR, though.

[Dakostu]

Doing that right now as we speak.