How can I attach a default sms template text to a specific contact number?
chompSMS by Delicious Inc. available from Google Play Store.


  with lots of extra features like Quick Reply, Quick Compose, Scheduled Messages, Passcode Lock, Privacy, Easy Pick Emoji's, Templates (text snippets), Signatures, heaps of customization options (notifications, ringtones, colors, fonts, wallpapers), Blacklisting and much more!


May diverge a bit from your precise goal, but works like a charm to achieve the same end.

You can use this app to have a ton of templates prepared, and use them when texting someone.

Instead of typing over and over the same thing on different messages, either at the beginning, middle or end of a text, you just long tab the message body and pick up the desired template.