Add custom search engines in settings

[maximizemaxwell]

What does this PR do?

Solution to Issue #1756
This PR lets chat-ui users pick the web-search provider (Serper/Google, Bing, DuckDuckGo, …) from Settings → Search Engine. The selected provider is stored in user settings, persisted to MongoDB, and passed through the RAG pipeline so that every web-search tool-call queries the engine the user chose.

Part of #1756

• Send the list of available websearch providers from the back-end to the front-end in the load function.
• An extra field in user settings to store the chosen provider with the UI for it in the settings page.
• Modify the web search code to fetch the provider from user settings instead of the current function which just picks the first in a hardcoded order.

Who can review?

@nsarrazin could you review this PR?

[gmanskibiditoilet]

keep going bro, you almost nailed it and made this feature a reality!

[gmanskibiditoilet]

@nsarrazin please check this PR to see if this feature works.

[nsarrazin]

Hi thanks for the contrib! Let me take a quick look

[gmanskibiditoilet]

almost there!

[gmanskibiditoilet]

Please note that this feature may not work due to the emergence of this issue #1812 , please fix this issue as well. it may affect the outcome of this PR because the search engine may not be able to detect information from the internet as issue #1812 has mentioned.

[gmanskibiditoilet]

@nsarrazin please review this PR once more. it is under pending.

[nsarrazin]

Hey @gmanskibiditoilet ! You've been posting under a lot of different issues lately, I just want to say I read everything and you really don't need to ping me on everything. I'm aware of what's on the board and I do my own prioritization. If you care about a feature, use the thumbs up reaction so I know it's important to you but you don't need to post every day, each time you do it I get an email notification 😅

[gmanskibiditoilet]

Hey @gmanskibiditoilet ! You've been posting under a lot of different issues lately, I just want to say I read everything and you really don't need to ping me on everything. I'm aware of what's on the board and I do my own prioritization. If you care about a feature, use the thumbs up reaction so I know it's important to you but you don't need to post every day, each time you do it I get an email notification 😅

alr, thanks for the notice