oh boy, this is really useful! I wonder why whatsapp folks haven't made this native, something like add a number to the app itself instead of relying solely on your phone contacts
I found WordPress plugins to be a bit of a race to the bottom for many ideas (eg: something is already doing it for free) but I imagine there is a great market for enterprisey plugins.
There are also some excellent plugin markets for most eCommerce platforms if you've got the drive to develop in them. Companies using an eComm platform are likely to be actual businesses so they are willing to spend more money for a quality plugin.
Yes, the low hanging fruit has been plucked, sometimes a dozen times. But if you think of WordPress as a very simple method of self-hosting, there are lots of apps that have yet to be built.
The other option is building a SaaS app and using a single WordPress install or WordPress multisite as the platform. I thought this was a crazy idea a couple years ago. Now I know of dozens of apps that have WordPress as the back-end, and it works well.
Learn normalisation from wikipedia, then read "The Art of SQL" to get a feeling for the shape of the weirdnesses, then read the postgresql documentation from end to end.
(disclaimer: worked for me, may not for anybody else)
I intend to read the PostgreSQL docs end to end at some point, but last time I checked the full PDF comes out to something like 3600 pages! I am astounded by the quality of everything about PostgreSQL, the community included.
You should be able to install it through the "Load unpacked extension..." button if you have the "Developer mode" checkbox selected on the chrome://extensions page.
I've faced this exact scenario a few months back when I asked some questions on Preact's Gitter. Pathetic. English is not even my first language, I swear I didn't know I'd be offending someone by saying "hey guys" :/