109 agenda session registrations

[rbento1096]

closes #109 closes #111 relates to #78

Once merged we will do some graphical improvements and bug fixing if required and then we can merge into prod.

things to improve (this PR or a new issue):

• some @todos in the sessions page (i.e. we need to open the detail in a modal for mobile) + when pressing a button it automatically selects the session (ev.preventDefault() not working for some reason...). + other minor things.

• Some graphical improvements can be made to most lists (both entity lists as well as the lists inside entity details).

  • example: Organizations page could use a grid with ion-card dispalying the company logo. Same for Speakers
  • example: Room detail page has a list with ion-items with too much space, we can reduce margins and add more content and color to the list (session code, etc..). Also check if the links work, there is no session/sessionId page

• to ask:

  • should we hide past sessions? maybe on toggle?
  • can users favorite sessions without registering?
  • should the session detail page include a list of the participants in the session (it has the needed data for that)

[rbento1096]

@uatisdeproblem from your review I have resolved those that have been fixed in recent commits. The other comments I agree with them but maybe it is better to make them after the event so as not to risk breaking anything. At least those related to data.

I created the issue #126 to keep track of these. If instead, you feel that there is no risk and they are easily doable in the next issues (the pipes for example). feel free to do it, just let me know so I can resolve the comments here :)

Thank you a lot for your help!