mod_http_oauth2: Tweak fallback error text Since the oauth error is more like the error condition, a symbolic error code, not the most human-friendly. Many error cases do have human-readable error descriptions that should be fine on their own, or changed to be. As a fallback, capitalize the error name.

This module lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
modules_enabled = {
    -- other modules --
    "s2s_whitelist",

}
s2s_whitelist = {
    "example.org",
}
```