"New Source" option gone for existing feed types

Hey, Chriz. Just to clarify, we have been set at 3x-dev. On production, we were running off a build that happened on 12/23/21. This config export should represent whatever commit was at the HEAD of that branch at that time. I'm not totally sure if that's the same as the Alpha 11 build.

uuid: b61f01c5-2c45-4793-a62f-d809288e9ffc
langcode: en
status: true
dependencies:
  config:
    - core.base_field_override.node.our_agency_tracking.title
    - field.field.node.our_agency_tracking.field_at_agency_id
    - field.field.node.our_agency_tracking.field_at_anticipated_comp_date
    - field.field.node.our_agency_tracking.field_at_applicant_name
    - field.field.node.our_agency_tracking.field_at_app_award_amount
    - field.field.node.our_agency_tracking.field_at_app_number
    - field.field.node.our_agency_tracking.field_at_commencement_date
    - field.field.node.our_agency_tracking.field_at_contract_executed
    - field.field.node.our_agency_tracking.field_at_grant_money_dispersed
    - field.field.node.our_agency_tracking.field_at_latitude
    - field.field.node.our_agency_tracking.field_at_longitude
    - field.field.node.our_agency_tracking.field_at_press_ready_description
    - field.field.node.our_agency_tracking.field_at_program_name
    - field.field.node.our_agency_tracking.field_at_project_name
    - field.field.node.our_agency_tracking.field_at_region
    - field.field.node.our_agency_tracking.field_at_round_key
    - field.field.node.our_agency_tracking.field_at_round_number
    - field.field.node.our_agency_tracking.field_project_status_color_
    - node.type.our_agency_tracking
  module:
    - node
    - redc_feed
_core:
  default_config_hash: kHJ6Z5xxsvNAfzQkV5q7ekhmXMlNtWa4E5r7SweX7FI
id: agency_tracking
label: 'Agency Tracking'
description: ''
help: ''
import_period: 604800
fetcher: http
fetcher_configuration:
  auto_detect_feeds: false
  use_pubsubhubbub: false
  always_download: false
  fallback_hub: ''
  request_timeout: 30
parser: tracking
parser_configuration: {  }
processor: 'entity:node'
processor_configuration:
  langcode: en
  update_existing: 2
  update_non_existent: 'entity:unpublish_action:node'
  expire: -1
  owner_feed_author: true
  owner_id: 0
  authorize: true
  skip_hash_check: true
  values:
    type: our_agency_tracking
custom_sources: {  }
mappings:
  -
    target: field_at_grant_money_dispersed
    map:
      value: grant_money_dispersed_to_date
  -
    target: field_at_app_award_amount
    map:
      value: app_award_amount
  -
    target: field_at_round_number
    map:
      value: round_number
    unique: {  }
  -
    target: field_at_press_ready_description
    map:
      value: press_ready_description
  -
    target: field_at_latitude
    map:
      value: latitude
  -
    target: title
    map:
      value: applicant_program_id
    unique:
      value: '1'
  -
    target: field_at_anticipated_comp_date
    map:
      value: anticipated_completion_date
    settings:
      timezone: UTC
  -
    target: field_at_contract_executed
    map:
      value: contract_executed
    settings:
      timezone: UTC
  -
    target: field_at_commencement_date
    map:
      value: commencement_date
    settings:
      timezone: UTC
  -
    target: field_at_round_key
    map:
      value: round_key
  -
    target: field_at_app_number
    map:
      value: app_number
    unique: {  }
  -
    target: field_at_longitude
    map:
      value: longitude
  -
    target: field_at_agency_id
    map:
      target_id: agency_id
    settings:
      reference_by: name
      autocreate: '1'
  -
    target: field_at_applicant_name
    map:
      value: applicant_name
    unique: {  }
  -
    target: field_at_region
    map:
      value: region
  -
    target: field_at_project_name
    map:
      value: project_name
    unique: {  }
  -
    target: field_at_program_name
    map:
      value: program_name
    unique: {  }
  -
    target: field_project_status_color_
    map:
      value: project_status
    unique: {  }

Hey, Chriz.

It does appear that this site is using a custom parser. That's quite vexing. I appreciate your help on this. Some new fields I'm adding weren't being inserted and now I know why.

As to the other issue, right now the parser is using the following:

```
class TrackingParser extends PluginBase implements ParserInterface {
```

Thanks for your work on this @MegaChriz. I'll add it to my to-do list.

Hey, @MegaChriz!

In my local environment, I have switched my code to reference the fork commit and run updb from the db export from production. The option "New Blank Source" now appears in the Source dropdown on the mappings page and I can add one without error. Success!

I did notice that updb doesn't create entries on the "custom sources" tab for the existing sources, though. Shouldn't it be? Note that it's possible that I threw a monkey in the works because, in production, I had created a couple while it was set to the 3x-dev branch. So it's posible that the update script looked at our feed type, saw that there were greater than zero custom sources in there, and decided not to run that part of the update. Not sure.