Describe the bug
When i am on the conference page, and i am registering a meeting, the action states "register".

To Reproduce
Steps to reproduce the behavior:

1. Go to main conference page (ex: https://alpha.try.decidim.org/conferences/Toy-Story-5)
2. Scroll down to Register
3. See text "Register for the conference"
4. click "register"
5. Select registration type (and make sure the button states "Attending" )
6. Go back to the previous page & refresh
7. See the Button states "Register"

Expected behavior
Since i already registered, I am expecting to see other caption on the button (ex: Manage registration), maybe also the button to have a different style.
I would have expected the Icon and label "Register for the conference" to be on the same line

Screenshots

Extra data (please complete the following information):

• Device: [e.g. iPhone6, Desktop]
• Device OS: [e.g. iOS8.1, Windows 10]
• Browser: [e.g. Chrome, Firefox, Safari]
• Decidim Version: 0.28.0.dev
• Decidim installation: Alpha Try Decidim

Additional context
Add any other context about the problem here.