Use shortcode_atts in `wp_biblelink_shortcode()

[paulgibbs]

In wp_biblelink_shortcode(), you currently parse a string like "John 3:16" and split that up into relevant parts. While this works, it's a bit of a brittle approach in case you ever decide to change the input format, and though this might seem an obvious input format to you, perhaps it mightn't be for others?

A more conventional way for shortcodes to accept multiple parameters is to use WordPress' Shortcode_API() function. The shortcode could look something like [bible book="1samuel" chapter="1" verse="1"]. See https://codex.wordpress.org/Shortcode_API for documentation and more examples.

If you think specifying the input as "John 3:16" is absolutely the way to go, I'd still recommend first using the shortcodes attributes function to parse the input, and then we can re-implement parsing simple strings such as "John 3:16" against that -- happy to help with advice when you get there.