Fix channel thumbnail upload

[rtibbles]

Description

Fixes the behaviour for saving thumbnail_encoding data to the server. As we are using a patch update for this, it does not get passed through the 'toJSON' method of the Channel Model on the frontend, and so is not getting JSON.stringified. Does away with the need for this by storing this data on the backend as a postgres JSONField.

Before/After Screenshots (if applicable)

Before:

After:

Steps to Test

• Open the channel details tab
• Click 'Edit Details'
• Upload a new thumbnail
• Save your changes
• See no flappy bird/async error

Checklist

• Is the code clean and well-commented?
• Are there tests for this change?
• Are the migrations safe for a large db (if applicable)?

Comments

Need to test the last checklist item before merging. This involves individual operations on each channel, so may be very slow.

[rtibbles]

Looks like I was forced to follow the advice for altering a column:
Change the type of a column | Add a new column, change the code to write to both columns, and backfill the new column

I don't think we'll lose data for not making the code write to both the columns, because the bug is preventing this writing anyway, so it will not take effect until it is deployed.

[lyw07]

Deployed the code to develop studio.
Got this error when running python manage.py migrate:

root@develop-studio-986877f88-ljcz8:/contentcuration# python contentcuration/manage.py migrate       
Operations to perform:
  Apply all migrations: admin, auth, authtoken, content, contentcuration, contenttypes, sessions, sites
Running migrations:
  Applying contentcuration.0003_copy_data...Traceback (most recent call last):
  File "contentcuration/manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/special.py", line 193, in database_forwards
    self.code(from_state.apps, schema_editor)
  File "/contentcuration/contentcuration/contentcuration/migrations/0003_copy_data.py", line 13, in forwards
    channel.thumbnail_encoding_json = json.loads(channel.thumbnail_encoding) if channel.thumbnail_encoding else {}
  File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 380, in raw_decode
    obj, end = self.scan_once(s, idx)
ValueError: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

[micahscopes]

This is really thorough, Richard!

💯

[rtibbles]

[micahscopes]

The most interesting pull request in the world!