Added automatic identification of "og:url" content through $location

[gustavoramos00]

If the content of "og:url" meta is empty, automatically detect the URL using $location.absUrl() service.

Disclaimer
I found this change very usefull in my project. But, I'm not JS specialist, so I don't know if this is the best approach to resolve this problem.

This is my first Pull Request in github.

[jvandemo]

@gustavoramos00 — Thank you for your contribution. Congrats on your first contribution 👍

Just to make sure I understand correctly, if you have:

<meta property="og:url" content="http://some.url"></meta>

you would then use:

<update-meta property="og:url" content=""></update-meta>

in a template to replace it with the absolute url of the current location?

Do I understand correctly? Thanks!

[gustavoramos00]

Exactly @jvandemo ! I tested as bellow, don't know if has difference.

<update-meta property="og:url"></update-meta>

Sorry for the delay in reply.

[jvandemo]

I'm really hesitant on this one. I like the idea but I'm not sure if it is explicit enough.

One may see unexpected side-effects when a website is hosted on multiple domains.

Maybe a more explicit approach where $location.absUrl() is explicitly specified as the value could be more transparent in case you really want to do this.

Great work on the PR though @gustavoramos00 👍

I'll leave it open for others to share their opinion. If no one else has an interest in this then I will close it in a month.

Thanks again @gustavoramos00!

[gustavoramos00]

Good point, @jvandemo. Even whether this behavior occurs only when no URL is provided, it doesn't seem explicit enough. What do you think about add other attribute, like this?

<update-meta property="og:url" use-abs-url="true"></update-meta>

[jvandemo]

@gustavoramos00 — The attribute is an interesting approach indeed. Curious to hear what others think. Nice work!