Add CloudAMQP billing plugin

manifest

@@ -3,3 +3,4 @@
 datadog
 mongodb-atlas
 openai
+cloudamqp

pkg/plugins/cloudamqp/README.md

@@ -0,0 +1,44 @@
+# CloudAMQP OpenCost Plugin
+
+The CloudAMQP plugin imports CloudAMQP Customer API invoice data into OpenCost Custom Costs.
+
+It uses the Customer API invoice endpoint:
+
+```text
+GET /invoices/period?year=<year>&month=<month>
+```
+
+CloudAMQP invoices are monthly, so the plugin downloads each required monthly invoice once per OpenCost request and prorates invoice line totals across daily Custom Cost windows.
+
+## Configuration
+
+Create a plugin config JSON file:
+
+```json
+{
+  "api_key": "<cloudamqp-customer-api-key>",
+  "log_level": "info"
+}
+```
+
+Optional fields:
+
+```json
+{
+  "api_base_url": "https://customer.cloudamqp.com/api",
+  "account_name": "cloudamqp",
+  "currency": "USD"
+}
+```
+
+The Customer API uses HTTP Basic Auth with an empty username and the API key as the password.
+
+## Cost Mapping
+
+- invoice line `amount`, `total`, `subtotal`, `price`, or `cost` -> monthly line amount
+- monthly line amount divided by days in the month -> daily billed and list cost
+- invoice `currency` -> response currency
+- invoice customer name -> account name and account ID
+- invoice line description/name/plan/product -> resource fields
+
+If invoice line amounts are not present, the plugin falls back to prorating the invoice `total`.

pkg/plugins/cloudamqp/cloudamqpplugin/cloudamqpconfig.go

@@ -0,0 +1,48 @@
+package cloudamqpplugin
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"strings"
+)
+
+const DefaultAPIBaseURL = "https://customer.cloudamqp.com/api"
+
+type CloudAMQPConfig struct {
+	APIKey      string `json:"api_key"`
+	APIBaseURL  string `json:"api_base_url"`
+	AccountName string `json:"account_name"`
+	Currency    string `json:"currency"`
+	LogLevel    string `json:"log_level"`
+}
+
+func GetCloudAMQPConfig(configFilePath string) (*CloudAMQPConfig, error) {
+	bytes, err := os.ReadFile(configFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("error reading CloudAMQP config file at %s: %v", configFilePath, err)
+	}
+
+	var result CloudAMQPConfig
+	if err := json.Unmarshal(bytes, &result); err != nil {
+		return nil, fmt.Errorf("error unmarshaling CloudAMQP config: %v", err)
+	}
+
+	if strings.TrimSpace(result.APIKey) == "" {
+		return nil, fmt.Errorf("api_key is required")
+	}
+	if strings.TrimSpace(result.APIBaseURL) == "" {
+		result.APIBaseURL = DefaultAPIBaseURL
+	}
+	if strings.TrimSpace(result.AccountName) == "" {
+		result.AccountName = "cloudamqp"
+	}
+	if strings.TrimSpace(result.Currency) == "" {
+		result.Currency = "USD"
+	}
+	if strings.TrimSpace(result.LogLevel) == "" {
+		result.LogLevel = "info"
+	}
+
+	return &result, nil
+}

pkg/plugins/cloudamqp/cloudamqpplugin/cloudamqpconfig_test.go

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+package cloudamqpplugin
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestGetCloudAMQPConfigDefaults(t *testing.T) {
+	path := writeConfig(t, `{"api_key": "test-key"}`)
+
+	config, err := GetCloudAMQPConfig(path)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if config.APIBaseURL != DefaultAPIBaseURL {
+		t.Fatalf("unexpected api base url: %s", config.APIBaseURL)
+	}
+	if config.AccountName != "cloudamqp" {
+		t.Fatalf("unexpected account name: %s", config.AccountName)
+	}
+	if config.Currency != "USD" {
+		t.Fatalf("unexpected currency: %s", config.Currency)
+	}
+	if config.LogLevel != "info" {
+		t.Fatalf("unexpected log level: %s", config.LogLevel)
+	}
+}
+
+func TestGetCloudAMQPConfigValidatesRequiredFields(t *testing.T) {
+	path := writeConfig(t, `{}`)
+
+	_, err := GetCloudAMQPConfig(path)
+	if err == nil {
+		t.Fatalf("expected validation error")
+	}
+}
+
+func writeConfig(t *testing.T, contents string) string {
+	t.Helper()
+
+	path := filepath.Join(t.TempDir(), "config.json")
+	if err := os.WriteFile(path, []byte(contents), 0600); err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+	return path
+}