SSA: prevent usage of Extract calls via forbidigo

Client-side extract calls depend on `managedFields`, which might not be
available. Therefore they should not be used in production code.

They are okay in test files (because the API has to be tested), in the
generated code (because the various type specific APIs still need to be
provided) and in unstructured.go (same reason).

hack/golangci-strict.yaml

@@ -25,10 +25,16 @@ issues:
     - linters:
        - ginkgolinter
       text: use a function call in (Eventually|Consistently)
+    # SSA Extract calls are allowed in tests.
+    - linters:
+       - forbidigo
+      text: should not be used because managedFields was removed
+      path: _test.go$
 
 linters:
   disable-all: false # in contrast to golangci.yaml, the default set of linters remains enabled
   enable: # please keep this alphabetized and in sync with golangci.yaml
+    - forbidigo
     - ginkgolinter
     - gocritic
     - govet
@@ -45,6 +51,15 @@ linters-settings: # please keep this alphabetized
       path: ../_output/local/bin/logcheck.so
       description: structured logging checker
       original-url: k8s.io/logtools/logcheck
+  forbidigo:
+    analyze-types: true
+    forbid:
+    - p: ^managedfields\.ExtractInto$
+      pkg: ^k8s\.io/apimachinery/pkg/util/managedfields$
+      msg: should not be used because managedFields was removed
+    - p: \.Extract
+      pkg: ^k8s\.io/client-go/applyconfigurations/
+      msg: should not be used because managedFields was removed
   gocritic:
   staticcheck:
     checks:

hack/golangci.yaml

@@ -26,10 +26,16 @@ issues:
     - linters:
        - ginkgolinter
       text: use a function call in (Eventually|Consistently)
+    # SSA Extract calls are allowed in tests.
+    - linters:
+       - forbidigo
+      text: should not be used because managedFields was removed
+      path: _test.go$
 
 linters:
   disable-all: true # not disabled in golangci-strict.yaml
   enable: # please keep this alphabetized and in sync with golangci-strict.yaml
+    - forbidigo
     - ginkgolinter
     - gocritic
     - govet
@@ -46,6 +52,15 @@ linters-settings: # please keep this alphabetized
       path: ../_output/local/bin/logcheck.so
       description: structured logging checker
       original-url: k8s.io/logtools/logcheck
+  forbidigo:
+    analyze-types: true
+    forbid:
+    - p: ^managedfields\.ExtractInto$
+      pkg: ^k8s\.io/apimachinery/pkg/util/managedfields$
+      msg: should not be used because managedFields was removed
+    - p: \.Extract
+      pkg: ^k8s\.io/client-go/applyconfigurations/
+      msg: should not be used because managedFields was removed
   gocritic:
     enabled-checks:             # not limited in golangci-strict.yaml
       - equalFold               # not limited in golangci-strict.yaml