Add and improve the sharing behaviour with Facebook (or any supported OpenGraph site)

[CloCkWeRX]

Related: #733 #556

We have the ability to add a 'share on facebook' mechanism without needing the API key or anything like that.

Part 1:
We want to implement either of

• https://developers.facebook.com/docs/plugins/share-button
• https://developers.facebook.com/docs/plugins/like-button

Part 2:
Refactor the meta tags for each significant area being shared - Garden, User, Plant, Seed, etc - and populate an appropriate title, image, description etc.

Part 3: Assess which other opengraph consuming sites we want to add if any. For example, google+ consumes the current opengraph tags.

http://stackoverflow.com/questions/10397510/do-services-other-than-facebook-use-open-graph discusses this in a bit more depth.

http://support.addthis.com/customer/portal/articles/381237-third-party-buttons might be a good example of an 'all in one' solution

[yifeiwu]

I used this gem for one of my projects. Would that work?
https://github.com/huacnlee/social-share-button

[CloCkWeRX]

It would for rendering the buttons (we do have assets for these already though), but not for adding useful metadata in the header tags so much.

[CloCkWeRX]

Warnings to fix up:

Share App ID Missing

The 'fb:app_id' property should be explicitly provided, Specify the app ID so that stories shared to Facebook will be properly attributed to the app. Alternatively, app_id can be set in url when open the share dialog.

and

Image Unavailable
Provided og:image, https://farm6.staticflickr.com/5556/15135715585_3ca67270d7_q.jpg could not be downloaded because it exceeded the maximum allowed sized of 8Mb or your server was too slow to respond.

which explains why sometimes we get a thumbnail, sometimes not.

[CloCkWeRX]

So I think this is pretty close to doable now - we have a fb app id, all of the opengraph stuff, etc - just need the social share buttons