Docoment a bit more about the IssuerConfig

Signed-off-by: Maartje Eyskens <maartje@eyskens.me>

pkg/apis/certmanager/v1/types_issuer.go

@@ -93,6 +93,8 @@ type IssuerSpec struct {
 	IssuerConfig `json:",inline"`
 }
 
+// IssuerConfig includes any configuration required for the issuer.
+// only one of these can be set per issuer.
 type IssuerConfig struct {
 	// ACME configures this issuer to communicate with a RFC8555 (ACME) server
 	// to obtain signed x509 certificates.

pkg/apis/certmanager/v1alpha2/types_issuer.go

@@ -89,6 +89,8 @@ type IssuerSpec struct {
 	IssuerConfig `json:",inline"`
 }
 
+// IssuerConfig includes any configuration required for the issuer.
+// only one of these can be set per issuer.
 type IssuerConfig struct {
 	// ACME configures this issuer to communicate with a RFC8555 (ACME) server
 	// to obtain signed x509 certificates.

pkg/apis/certmanager/v1alpha3/types_issuer.go

@@ -89,6 +89,8 @@ type IssuerSpec struct {
 	IssuerConfig `json:",inline"`
 }
 
+// IssuerConfig includes any configuration required for the issuer.
+// only one of these can be set per issuer.
 type IssuerConfig struct {
 	// ACME configures this issuer to communicate with a RFC8555 (ACME) server
 	// to obtain signed x509 certificates.

pkg/apis/certmanager/v1beta1/types_issuer.go

@@ -91,6 +91,8 @@ type IssuerSpec struct {
 	IssuerConfig `json:",inline"`
 }
 
+// IssuerConfig includes any configuration required for the issuer.
+// only one of these can be set per issuer.
 type IssuerConfig struct {
 	// ACME configures this issuer to communicate with a RFC8555 (ACME) server
 	// to obtain signed x509 certificates.