fix: wire allow_custom_*_config flags from settings to DoclingConverterManagerConfig

[pvliesdonk]

vlm_pipeline_custom_config (and its picture-description and code/formula siblings) always raises a 422 error claiming custom configuration is not allowed, even when an administrator intends to permit it. There is no environment variable that actually enables these features.

Root cause: DoclingConverterManagerConfig in docling-jobkit has three admin-facing flags:

• allow_custom_vlm_config (default False)
• allow_custom_picture_description_config (default False)
• allow_custom_code_formula_config (default False)

Neither instantiation site in docling-serve (orchestrator_factory.py, __main__.py) passes these flags, so they are permanently False regardless of any environment variable.

Fix: Add the three fields to DoclingServeSettings, which pydantic-settings maps to env vars automatically:

• DOCLING_SERVE_ALLOW_CUSTOM_VLM_CONFIG
• DOCLING_SERVE_ALLOW_CUSTOM_PICTURE_DESCRIPTION_CONFIG
• DOCLING_SERVE_ALLOW_CUSTOM_CODE_FORMULA_CONFIG

Then pass them through in both DoclingConverterManagerConfig instantiation sites. This follows the identical pattern established for allow_external_plugins in #328.

Also updates docs/configuration.md to document the three new env vars.

Issue resolved by this Pull Request:
Resolves #526

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[dosubot]

Documentation Updates

2 document(s) were updated by changes in this PR:

How can I use Docling's REST API to convert a PDF from a URL to Markdown with OpenAI-generated image descriptions, and is base64 encoding required for URL sources?

View Changes

@@ -14,7 +14,7 @@
 | `to_formats` | list | Output formats. Example: `["md"]`. |
 | `do_picture_description` | bool | If enabled, describe pictures in documents. Boolean. Optional, defaults to false. |
 | `picture_description_preset` | str or null | Preset ID for picture description. Recommended for most users. |
-| `picture_description_custom_config` | dict or null | Custom configuration for picture description (advanced). **Requires administrator permission** - see note below. |
+| `picture_description_custom_config` | dict or null | Custom configuration for picture description (advanced). **Requires administrator permission** - see note above. |
 | `picture_description_api` | dict or null | **DEPRECATED**: API details for using a vision-language model in the picture description. Please migrate to `picture_description_preset` or `picture_description_custom_config`. |
 | `picture_description_area_threshold` | float | Minimum percentage of the area for a picture to be processed with the models. |
 | `image_alt_mode` | str | Controls how alt text is generated for images: `static`, `caption`, or `description`. |

How can you use Docling's REST API to convert a PDF to Markdown and generate image descriptions using an OpenAI model?

View Changes

@@ -78,12 +78,12 @@
 > 
 > Custom configuration parameters require administrator permission to use. By default, these features are disabled for security reasons.
 > 
-> **To enable custom configurations, your administrator must set:**
-> - `DOCLING_SERVE_ALLOW_CUSTOM_PICTURE_DESCRIPTION_CONFIG=true` for custom picture description configs
-> - `DOCLING_SERVE_ALLOW_CUSTOM_VLM_CONFIG=true` for custom VLM pipeline configs  
-> - `DOCLING_SERVE_ALLOW_CUSTOM_CODE_FORMULA_CONFIG=true` for custom code/formula configs
+> **To enable custom configurations, your administrator must set these environment variables:**
+> - `DOCLING_SERVE_ALLOW_CUSTOM_PICTURE_DESCRIPTION_CONFIG=true` — Enables `picture_description_custom_config`
+> - `DOCLING_SERVE_ALLOW_CUSTOM_VLM_CONFIG=true` — Enables `vlm_pipeline_custom_config`
+> - `DOCLING_SERVE_ALLOW_CUSTOM_CODE_FORMULA_CONFIG=true` — Enables `code_formula_custom_config`
 > 
-> If these environment variables are not enabled, attempting to use `picture_description_custom_config`, `vlm_pipeline_custom_config`, or `code_formula_custom_config` will result in a **422 error**.
+> When set to `false` (the default), only presets are accepted. If these environment variables are not enabled, attempting to use the respective custom configuration parameters will result in a **422 error**.
 > 
 > **Contact your Docling Serve administrator if you need access to custom configuration options.**
 

^{How did I do? Any feedback?}  

[dolfim-ibm]

lgtm