Change variout CharField types to TextField instead

In a number of places we're using fixed-width text fields without
needing too, and it's causing problems.

Noticed in the case of Notificationcallback.url, then looked for
others where the fixed-width makes no apparent sense. *Not* changing
any fields tagged with primary_key=True - leave those alone.

Closes #273

Signed-off-by: Steve McIntyre <steve.mcintyre@linaro.org>
15 jobs for switch-notifications-textfield in 5 minutes and 28 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #43340
amd64
dispatcher-debian-10

00:02:53

passed #43338
amd64
dispatcher-debian-9

00:03:13

passed #43341
amd64
server-debian-10

00:01:52

passed #43339
amd64
server-debian-9

00:02:12

 
  Analyze
failed #43343
amd64
black

00:00:29

passed #43345
amd64
code_quality

00:00:22

passed #43344
amd64
codestyle

00:00:36

passed #43347
amd64
job-schema

00:00:42

passed #43346
amd64
pylint

00:02:14

passed #43342
amd64-dind allowed to fail
sast

00:01:53

 
  Build
skipped #43350
amd64
amd64/pkg-debian-10
skipped #43349
amd64
amd64/pkg-debian-9
skipped #43348
amd64
doc
 
  Docker
skipped #43351
amd64-dind
amd64/lava-dispatcher
skipped #43352
amd64-dind
amd64/lava-server
 
Name Stage Failure
failed
black Analyze
Skipping Git submodules setup
$ ./.gitlab-ci/$CI_JOB_STAGE/$CI_JOB_NAME.sh setup
nothing to do
$ ./.gitlab-ci/$CI_JOB_STAGE/$CI_JOB_NAME.sh
+ LC_ALL=C.UTF-8 LANG=C.UTF-8 black --exclude dashboard_app --check .
would reformat /builds/steve/lava/lava_scheduler_app/models.py
All done! 💥 💔 💥
1 file would be reformatted, 415 files would be left unchanged.
ERROR: Job failed: exit code 1