refactor: http interfaces (#114)

* implement custom http handler interface

* implement trace_id

* normalize http method spacing for consistent logs

* fix failing test

* fix linter errors

* cleanup old dead code

* more route cleanup

* cleanup some inconsistent errors

* update and generate code

* make taskfile more consistent

* update task calls

* run tidy

* drop `@` tag for version

* use relative paths

* tidy

* fix auto-setting variables

* update build paths

* add contributing guide

* tidy

backend/internal/sys/validate/errors.go

@@ -0,0 +1,119 @@
+package validate
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type UnauthorizedError struct {
+}
+
+func (err *UnauthorizedError) Error() string {
+	return "unauthorized"
+}
+
+func IsUnauthorizedError(err error) bool {
+	var re *UnauthorizedError
+	return errors.As(err, &re)
+}
+
+func NewUnauthorizedError() error {
+	return &UnauthorizedError{}
+}
+
+type InvalidRouteKeyError struct {
+	key string
+}
+
+func (err *InvalidRouteKeyError) Error() string {
+	return "invalid route key: " + err.key
+}
+
+func NewInvalidRouteKeyError(key string) error {
+	return &InvalidRouteKeyError{key}
+}
+
+func IsInvalidRouteKeyError(err error) bool {
+	var re *InvalidRouteKeyError
+	return errors.As(err, &re)
+}
+
+// ErrorResponse is the form used for API responses from failures in the API.
+type ErrorResponse struct {
+	Error  string `json:"error"`
+	Fields string `json:"fields,omitempty"`
+}
+
+// RequestError is used to pass an error during the request through the
+// application with web specific context.
+type RequestError struct {
+	Err    error
+	Status int
+	Fields error
+}
+
+// NewRequestError wraps a provided error with an HTTP status code. This
+// function should be used when handlers encounter expected errors.
+func NewRequestError(err error, status int) error {
+	return &RequestError{err, status, nil}
+}
+
+func (err *RequestError) Error() string {
+	return err.Err.Error()
+}
+
+// IsRequestError checks if an error of type RequestError exists.
+func IsRequestError(err error) bool {
+	var re *RequestError
+	return errors.As(err, &re)
+}
+
+// FieldError is used to indicate an error with a specific request field.
+type FieldError struct {
+	Field string `json:"field"`
+	Error string `json:"error"`
+}
+
+// FieldErrors represents a collection of field errors.
+type FieldErrors []FieldError
+
+func (fe FieldErrors) Append(field, reason string) FieldErrors {
+	return append(fe, FieldError{
+		Field: field,
+		Error: reason,
+	})
+}
+
+func (fe FieldErrors) Nil() bool {
+	return len(fe) == 0
+}
+
+// Error implments the error interface.
+func (fe FieldErrors) Error() string {
+	d, err := json.Marshal(fe)
+	if err != nil {
+		return err.Error()
+	}
+	return string(d)
+}
+
+func NewFieldErrors(errs ...FieldError) FieldErrors {
+	return errs
+}
+
+func IsFieldError(err error) bool {
+	v := FieldErrors{}
+	return errors.As(err, &v)
+}
+
+// Cause iterates through all the wrapped errors until the root
+// error value is reached.
+func Cause(err error) error {
+	root := err
+	for {
+		if err = errors.Unwrap(root); err == nil {
+			return root
+		}
+		root = err
+	}
+}