add title field to Job model

[imcaizheng]

• update ES mapping for the Job index
• update Joi schema

[maxceem]

@imcaizheng tested locally and works good.

[imcaizheng]

@maxceem Just in case, we may need to update existing ES server deployed for DEV similar with topcoder-platform/taas-apis#22 (comment)

[maxceem]

Thanks for pointing this out @imcaizheng. As per discussion in that ticket it looks like AWS ES doesn't support such commands, so for existent data, we would not have title for now. I think we have to create a script that would reindex all the data from DB to ES to handle such situations in the future.

[maxceem]

@imcaizheng but we still have to updated mapping, right?

[imcaizheng]

@maxceem Yes. It was confirmed by nkumar-topcoder that update mapping would work for AWS ES in this comment topcoder-platform/taas-apis#22 (comment).

It seems like a workaround for migrating data from DB to ES every time indices are modified, but it is quite a solution for now.