Harden cert provisioning failure and write-back

Rate limits no longer inflate ssl_retry_count into an instant FAILED
path. Centralize outcomes in decideProvisioningOutcome, keep ACME
order state on transient and rate-limit errors, bound each Process
tick with a timeout, and block on FOR UPDATE when persisting a
freshly issued certificate.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>
Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/certmanager/acme_test.go

@@ -0,0 +1,76 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+package certmanager
+
+import (
+	"errors"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/crypto/acme"
+)
+
+func TestNewACMEError_RateLimited(t *testing.T) {
+	t.Parallel()
+
+	err := newACMEError(
+		"cannot create order",
+		&acme.Error{
+			ProblemType: "urn:ietf:params:acme:error:rateLimited",
+			Detail:      "too many requests",
+			Header:      http.Header{"Retry-After": []string{"120"}},
+		},
+	)
+
+	require.NotNil(t, err)
+	assert.ErrorIs(t, err, ErrACMERateLimited)
+	assert.Equal(t, 2*time.Minute, err.RetryAfter())
+	assert.Equal(t, "urn:ietf:params:acme:error:rateLimited", err.problemType)
+	assert.Equal(t, "too many requests", err.detail)
+}
+
+func TestNewACMEError_RateLimitedDefaultCooldown(t *testing.T) {
+	t.Parallel()
+
+	err := newACMEError(
+		"cannot create order",
+		&acme.Error{ProblemType: "URN:IETF:PARAMS:ACME:ERROR:RATELIMITED"},
+	)
+
+	require.NotNil(t, err)
+	assert.ErrorIs(t, err, ErrACMERateLimited)
+	assert.Equal(t, defaultCooldown, err.RetryAfter())
+}
+
+func TestNewACMEError_NonRateLimited(t *testing.T) {
+	t.Parallel()
+
+	cause := errors.New("network timeout")
+	err := newACMEError("cannot get order", cause)
+
+	require.NotNil(t, err)
+	assert.False(t, errors.Is(err, ErrACMERateLimited))
+	assert.ErrorIs(t, err, cause)
+	assert.Equal(t, time.Duration(0), err.RetryAfter())
+}