Fix fallout from STRICT_TRANS_TABLES being on by default

[notartom]

With the move to Jammy, MariaDB gets STRICT_TRANS_TABLES on by default. This means that we need to be more careful around how we insert/update values. See for example c79a69d, wherein we can no longer insert the empty string into an integer column and have it get magically converted to the default 0, which I assume is what was happening before.

If we're ever inserting without specifying a value for a column, it needs to be declared as having a default (NULL), and since no automagic truncation is happening, we need to make sure our data can fit in our fields.

CREATE TABLE `form_generators` (
  <snip>
  `link_to_auth` varchar(255) NOT NULL,
  <snip>
) ENGINE=InnoDB AUTO_INCREMENT=13122 DEFAULT CHARSET=utf8mb3

So once the update is complete, but before we go live, we'll need to:

alter table form_generators modify column link_to_auth varchar(255) null;
alter table form_generators modify column pub_year int(4) null;
alter table search_table modify column section_reader_id int(11) null;
alter table search_table modify column search_field varchar(510) not null;
alter table users alter column max_projects set default 0;

update users set ip_address=0;
alter table users modify ip_address varchar(45) not null;
update users set ip_address='127.0.0.1' where ip_address='0';