LDAP: Move LDAP globals to Config (#63255)

* structure dtos and private methods

* add basic LDAP service

* use LDAP service in ldap debug API

* lower non fatal error

* remove unused globals

* wip

* remove final globals

* fix tests to use cfg enabled

* restructure errors

* remove logger from globals

* use ldap service in authn

* use ldap service in context handler

* fix failed tests

* fix ldap middleware provides

* fix provides in auth_test.go

pkg/services/ldap/api/errors.go

@@ -0,0 +1,11 @@
+package api
+
+import "fmt"
+
+type OrganizationNotFoundError struct {
+	OrgID int64
+}
+
+func (e *OrganizationNotFoundError) Error() string {
+	return fmt.Sprintf("unable to find organization with ID '%d'", e.OrgID)
+}