core/internal/kubernetes: refactor PKI fully

We move ad-hoc certificate/key creation to a little declarative,
future-inspired API.

The API is split into two distinct layers:
 - an etcd-backed managed certificate storage that understands server
   certificates, client certificates and CAs
 - a Kubernetes PKI object, that understands what certificates are
   needed to bring up a cluster

This allows for deduplicated path names in etcd, some semantic
information about available certificates, and is in general groundwork
for some future improvements, like:
 - a slightly higher level etcd 'data store' api, with
   less-stringly-typed paths
 - simplification of service startup code (there's a bunch of cleanups
   that can be still done in core/internal/kubernetes wrt. to
   certificate marshaling to the filesystem, etc)

Test Plan: covered by existing tests - but this should also now be nicely testable in isolation!

X-Origin-Diff: phab/D564
GitOrigin-RevId: a58620c37ac064a15b7db106b7a5cbe9bd0b7cd0
diff --git a/core/internal/kubernetes/pki/BUILD.bazel b/core/internal/kubernetes/pki/BUILD.bazel
new file mode 100644
index 0000000..e188bfa
--- /dev/null
+++ b/core/internal/kubernetes/pki/BUILD.bazel
@@ -0,0 +1,19 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "ca.go",
+        "certificate.go",
+        "kubernetes.go",
+    ],
+    importpath = "git.monogon.dev/source/nexantic.git/core/internal/kubernetes/pki",
+    visibility = ["//core:__subpackages__"],
+    deps = [
+        "//core/internal/common:go_default_library",
+        "@io_etcd_go_etcd//clientv3:go_default_library",
+        "@io_k8s_client_go//tools/clientcmd:go_default_library",
+        "@io_k8s_client_go//tools/clientcmd/api:go_default_library",
+        "@org_uber_go_zap//:go_default_library",
+    ],
+)