Content-Security-Policy: add strict csp headers and use a nonce

[abhiramtilakiiit]

Need for Changes

• The latest google lighthouse report has shown how we allow unsafe-inline styles and
  basically have no CSP in place.

According to nextjs docs it is recommended to add these headers to the middleware and wherever
needed (when external scripts or inline scripts are being called), add the nonce instead
to uniquely generate a nonce everytime the page loads.

• Since we are using MUI, their docs, instruct
  addind nonce to the ThemeRegistry using aa cache provider. (Update: We are having to use unsafe-inline because some MUI components use inline styles (mui github: issues/19938), we will remove this if it gets fixed upstream sometime).

Changes

• I have added some strict headers and made some changes so the redirects also return these headers.
• I have included the nonce in the ThemeRegistry style tag, and the subsequent CacheProvider to cache it out.
• I have added *.iiit.ac.in, as a white list to <iframe> as long as it is being displayed in the iiit website.

Todo

• There are some instances where CSP errors out, please pay close attention to the browser console.

[Dileepadari]

Looks good, testing with different components done, can be merged.