Refactor: clean up code smells from PR #151 (catch-expired-session)

[Copilot]

Code quality issues introduced in PR #151 across dataManager.element.js and mapbender.element.digitizer.js: duplicated fail-listener construction, an opaque IIFE-curried arrow, minor formatting/spacing inconsistencies, and a misleading comment.

Changes

• Extract _createFailListener(retryCallback) — the identical 3-line ternary guarding Mapbender.handleAjaxError vs _onAjaxError fallback was duplicated in _loadGrants, postJSON, and _getData; now lives in one place:

  _createFailListener: function (retryCallback) {
      // Mapbender.handleAjaxError only exists in Mapbender >= 4.2.5
      return typeof Mapbender.handleAjaxError === 'function'
          ? (e) => Mapbender.handleAjaxError(e, retryCallback)
          : this._onAjaxError.bind(this);
  },

• Simplify _loadGrants .then() callback — (mergeWith => allGrants => { ... })(this.options.schemes) replaced with a plain arrow function accessing this.options.schemes directly; the IIFE added no value since the callback already captures this.

• Spacing/formatting — onGrantsLoadStarted: function() → function () in both files; missing space before (response) in updateMultiple call.

• Comments — orphaned // setup() called in onGrantsLoadStarted expanded to trace the full call path; // can be overridden by digitizer generalised to // can be overridden by subclasses.

Original prompt

Everyhting good now. Now thoroughly look through the code and detct smells and everything else you would find worth fixing as a senior developer evaluating the PR. Only the things unique to this branch compared to develop

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

Created from VS Code.

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