Community PR: https://github.com/odoo/odoo/pull/189424

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PURPOSE
Users often create content with multiple sections marked by headings (especially in Knowledge). To ease the navigation and sharing, each heading should be treated as an anchor that users can get and share with others.

Users can easily obtain a link to any heading by simply clicking a anchor button next to the title. This link can then be used to navigate directly to the corresponding section.

SPEC
- Next to each heading, add the anchor button (with opacity, see icon - see https://fontawesome.com/v4/icon/link)
- By clicking to the anchor button, a link is copied into the user's clipboard, we update the URL of the browser too and we auto-scroll to this content
- The url contains a random hash to access the heading
- If anyone else with the right access clicks on this link, they are redirected to the content and the heading is highlighted a few ms

Enable the feature for knowledge only at this stage.

task-3595680

This commit introduces a new ai module as well as a bridge module ai_calendar.

This module allows for the creation of AI agents designed for retrieval-augmented generation (RAG), using context extracted from uploaded documents and web pages. Aside from answering questions, the agents can also perform actions on the database. Currently, they can create calendar events with users through integration with the calendar module.

This module also introduces one new dependency: `markdown2`.
- `markdown2` is used for converting the response of the LLM APIs from markdown to html for rendering in the chat messages.

As for the technical features of the module:
- Creation of AI agents that use models from various providers. The agents can be fine-tuned for specific tasks by specifying system prompts, and providing relevant documents.
- Indexation and chunking of documents (e.g. PDF, ppt, docs, etc.) and web pages for easy retrieval when creating the RAG.
- Integration with server actions to allow agents to perform operations directly within Odoo database.

Choices:
- Markdown library: two libraries were considered during development for the conversion of markdown to html: `markdown`, and `markdown2`. For this choice, we considered the performances and the features proposed by the two libraries. In terms of performance, `markdown` we conducted a benchmark that consisted in the conversion of a big markdown file (~2.3MB) from which `markdown` came out on top. However, when considering the features, `markdown2` proposes more features "out-of-the-box" and is also more robust for standard markdown, specifically for the use case of nested lists. Which is why we decided to work with `markdown2`

Limitations:
- The agents' backend currently only support two OpenAI models (GPT 3.5, and GPT 4).
- The AI actions are limited to scheduling of calendar events.
- Embedding generation is currently fixed to use the OpenAI API, requiring an OpenAI key, and the database column size for storing embeddings is predefined.

task-4526285

Co-authored-by: deimort <dpro@odoo.com>
Co-authored-by: abdelrahmanfawzy <abdh@odoo.com>
Co-authored-by: abdelrahmankhaledg <akha@odoo.com>
Co-authored-by: lobaudoux <lba@odoo.com>