ApiWrapper dirty flag handling

[BacLuc]

Vorschlag:

this.dirty = this.dirty || this.localValue !== this.apiValue

_Originally posted by @pmattmann in https://github.com/ecamp/ecamp3/pull/2572#discussion_r848768966_

1. Specify how ApiWrapper should handle beeing dirty
   • Proposal by @usu: similar behaviour like the drag and drop of contentnodes and waiting for the last request
2. Adapt the tests (maybe refactoring) that they reflect the specification
3. Implement the behaviour specified in the tests
4. Test in the frontend that the specified behaviour matches the needs of the users
5. Maybe adapt the tests
6. Implement
7. Repeat from 4

[usu]

Point 1 (behavior specification)

Initial behavior

• initially the field is not dirty (dirty=false)
• new values from the store are reflected in the local field value
• this behavior is the same, even when the field receives focus

Editing

• onInput the field is set to dirty and a sequence number or timestamp is saved
• from now on, new values from the store are not reflected in the local field value
• the dirty flag is reset when
  • an API request has successfully finished (no error)
  • AND: this API response belongs to last known dirty sequence/timestamp
  • AND: (the response-value is identical to the local field value) OR (the field has no focus anymore)

onBlur

• if no saving-cycle is ongoing (=no input happened since last API request finished)
• reset local field value to value from store
• reset dirty flag