update_devcontainer_db_host

# File railties/lib/rails/generators/rails/db/system/change/change_generator.rb, line 147
            def update_devcontainer_db_host
              container_env = devcontainer_json["containerEnv"]
              db_name = database.name

              if container_env["DB_HOST"]
                if database.service
                  container_env["DB_HOST"] = db_name
                else
                  container_env.delete("DB_HOST")
                end
              else
                if database.service
                  container_env["DB_HOST"] = db_name
                end
              end

              new_json = JSON.pretty_generate(container_env, indent: "  ", object_nl: "\n  ")

              gsub_file(".devcontainer/devcontainer.json", /("containerEnv"\s*:\s*)(.|\n)*?(^\s{2}})/, "\\1#{new_json}")
            end