feat: improve Event schema.org data

[rlespinasse]

• support 2 days conference
• fix location information
• support multiple offers
  • improve date information (valid and availability)
  • used Reserved as offer availability to reflect the current state of billetweb (will need to be changed to InStock later on)
  • add name for disambiguation between offers

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud