feat: view resource history over time

[scotwells]

This PR introduces a new history command that can be used to diff a resource over time. This is helpful for analyzing what changes were made to a resource and who made the change.

What's shown here is an example of running the command against a resource in Datum Cloud so we could analyze the changes one of our system components was making to a resource.

▶ ./datumctl activity --project another-project-w24uyl history dnsrecordsets dns-record-set-www-ibm-com-5npagr-qp25o9 --diff

╭─────────────────────────────────────────────────────────────╮
│ Change #1   📝 patch    [200]
│ 🕐 2026-01-21 09:29:35
│ 👤 dns-operator
╰─────────────────────────────────────────────────────────────╯
📸 Initial state (oldest available change)

{
  "apiVersion": "dns.networking.miloapis.com/v1alpha1",
  "kind": "DNSRecordSet",
  "metadata": {
    "name": "dns-record-set-www-ibm-com-5npagr-qp25o9",
    "namespace": "default"
  },
  "spec": {
    ...
  },
  "status": {
    ...
  }
}

╭─────────────────────────────────────────────────────────────╮
│ Change #2   📝 patch    [200]
│ 🕐 2026-01-21 09:29:35
│ 👤 dns-operator
╰─────────────────────────────────────────────────────────────╯
📝 Changes: metadata only

--- Previous
+++ Current
@@ -143,7 +143,7 @@
     "conditions": [
       {
         "lastTransitionTime": "2025-12-03T10:10:17Z",
-        "message": "Record \"outer-global-dual.ibmcom-tls12.edgekey.net\": status 422: {\"error\": \"RRset outer-global-dual.ibmcom-tls12.edgekey.net.www.ibm.com. IN CNAME has more than one record\"}",
+        "message": "Record \"@\": status 422: {\"error\": \"RRset www.ibm.com. IN CNAME has more than one record\"}",
         "observedGeneration": 1,
         "reason": "PDNSError",
         "status": "False",

╭─────────────────────────────────────────────────────────────╮
│ Change #3   📝 patch    [200]
│ 🕐 2026-01-21 09:31:04
│ 👤 dns-operator
╰─────────────────────────────────────────────────────────────╯
📝 Changes: metadata only

--- Previous
+++ Current
@@ -143,7 +143,7 @@
     "conditions": [
       {
         "lastTransitionTime": "2025-12-03T10:10:17Z",
-        "message": "Record \"@\": status 422: {\"error\": \"RRset www.ibm.com. IN CNAME has more than one record\"}",
+        "message": "Record \"outer-global-dual.ibmcom-tls12.edgekey.net\": status 422: {\"error\": \"RRset outer-global-dual.ibmcom-tls12.edgekey.net.www.ibm.com. IN CNAME has more than one record\"}",
         "observedGeneration": 1,
         "reason": "PDNSError",
         "status": "False",

[ecv]

whoa that is cool