feat: uid and email should have unique contains/index in SQL DBs by default

[yurem]

We need to add uniqueness constrains for uid and email to SQL DB: MySQL/PostgreSQL/Spanner.

For some DB is preferable to use indexes for this. For example (PostgreSQL):

CREATE UNIQUE INDEX ON "jansPerson" ("uid");
CREATE UNIQUE INDEX ON "jansPerson" ("mail");

The reason for this that we already add these indexes to DB. Also I think there similar answers here.