Allow finalizing a poll by disallowing more votes

[binamkayastha]

User Story:

As a Poll Creator, I would like to finalize a poll by disallowing more votes, because I want to prevent changes to the poll after a choice has been made.

Figma Design

Acceptance Criteria:

• Implement conditional view on the voting page to only show a link to the results after the poll has been closed like "This poll is now closed/Voting on this poll is now stopped"
• Set Open For Voting property in Poll to be false
• Set endDate to the time the poll was closed (all timezones should be ISOFormat). End date should be generated server side
• Prevent votes from being allowed in the API if the poll is closed