Mango: support multiple server-side warnings

[willholley]

Overview

Changes the handling of mango warnings to support multiple warnings
delimited by a newline, as added in apache/couchdb#2410.

This also removes the client-side warning for too many docs scanned as that is now generated on the server.

Testing recommendations

When apache/couchdb#2410 is merged, run some Mango queries with bad / no indexes to generate warnings.

GitHub issue number

Related Pull Requests

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;
• Update rebar.config.script with the correct tag once a new Fauxton release is made

[Antonio-Maranhao]

This will print <br> instead of adding a line break. You can use this instead:

getWarning(warnings) {
    if (warnings) {
      const lines = warnings.split('\n').map((warnText, i) => {
        return <React.Fragment key={i}>{warnText}<br/></React.Fragment>;
      });
      return <span>{lines}</span>;
    }
  }

[willholley]

thanks @Antonio-Maranhao - updated with those changes

[willholley]

hmm - looks like CI against couchdb:dev is broken...