refactor: Break core package into multiple packages under config/endpoint (#759)

* refactor: Partially break core package into dns, result and ssh packages

* refactor: Move core package to config/endpoint

* refactor: Fix warning about overlapping imported package name with endpoint variable

* refactor: Rename EndpointStatus to Status

* refactor: Merge result pkg back into endpoint pkg, because it makes more sense

* refactor: Rename parameter r to result in Condition.evaluate

* refactor: Rename parameter r to result

* refactor: Revert accidental change to endpoint.TypeDNS

* refactor: Rename parameter r to result

* refactor: Merge util package into endpoint package

* refactor: Rename parameter r to result

config/endpoint/external_endpoint.go

@@ -0,0 +1,88 @@
+package endpoint
+
+import (
+	"errors"
+
+	"github.com/TwiN/gatus/v5/alerting/alert"
+)
+
+var (
+	// ErrExternalEndpointWithNoToken is the error with which Gatus will panic if an external endpoint is configured without a token.
+	ErrExternalEndpointWithNoToken = errors.New("you must specify a token for each external endpoint")
+)
+
+// ExternalEndpoint is an endpoint whose result is pushed from outside Gatus, which means that
+// said endpoints are not monitored by Gatus itself; Gatus only displays their results and takes
+// care of alerting
+type ExternalEndpoint struct {
+	// Enabled defines whether to enable the monitoring of the endpoint
+	Enabled *bool `yaml:"enabled,omitempty"`
+
+	// Name of the endpoint. Can be anything.
+	Name string `yaml:"name"`
+
+	// Group the endpoint is a part of. Used for grouping multiple endpoints together on the front end.
+	Group string `yaml:"group,omitempty"`
+
+	// Token is the bearer token that must be provided through the Authorization header to push results to the endpoint
+	Token string `yaml:"token,omitempty"`
+
+	// Alerts is the alerting configuration for the endpoint in case of failure
+	Alerts []*alert.Alert `yaml:"alerts,omitempty"`
+
+	// NumberOfFailuresInARow is the number of unsuccessful evaluations in a row
+	NumberOfFailuresInARow int `yaml:"-"`
+
+	// NumberOfSuccessesInARow is the number of successful evaluations in a row
+	NumberOfSuccessesInARow int `yaml:"-"`
+}
+
+// ValidateAndSetDefaults validates the ExternalEndpoint and sets the default values
+func (externalEndpoint *ExternalEndpoint) ValidateAndSetDefaults() error {
+	if err := validateEndpointNameGroupAndAlerts(externalEndpoint.Name, externalEndpoint.Group, externalEndpoint.Alerts); err != nil {
+		return err
+	}
+	if len(externalEndpoint.Token) == 0 {
+		return ErrExternalEndpointWithNoToken
+	}
+	for _, externalEndpointAlert := range externalEndpoint.Alerts {
+		if err := externalEndpointAlert.ValidateAndSetDefaults(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// IsEnabled returns whether the endpoint is enabled or not
+func (externalEndpoint *ExternalEndpoint) IsEnabled() bool {
+	if externalEndpoint.Enabled == nil {
+		return true
+	}
+	return *externalEndpoint.Enabled
+}
+
+// DisplayName returns an identifier made up of the Name and, if not empty, the Group.
+func (externalEndpoint *ExternalEndpoint) DisplayName() string {
+	if len(externalEndpoint.Group) > 0 {
+		return externalEndpoint.Group + "/" + externalEndpoint.Name
+	}
+	return externalEndpoint.Name
+}
+
+// Key returns the unique key for the Endpoint
+func (externalEndpoint *ExternalEndpoint) Key() string {
+	return ConvertGroupAndEndpointNameToKey(externalEndpoint.Group, externalEndpoint.Name)
+}
+
+// ToEndpoint converts the ExternalEndpoint to an Endpoint
+func (externalEndpoint *ExternalEndpoint) ToEndpoint() *Endpoint {
+	endpoint := &Endpoint{
+		Enabled:                 externalEndpoint.Enabled,
+		Name:                    externalEndpoint.Name,
+		Group:                   externalEndpoint.Group,
+		Alerts:                  externalEndpoint.Alerts,
+		NumberOfFailuresInARow:  externalEndpoint.NumberOfFailuresInARow,
+		NumberOfSuccessesInARow: externalEndpoint.NumberOfSuccessesInARow,
+	}
+	return endpoint
+}