feat: enable endpoint field on mistral conversation component

[sicoyle]

Description

Fix for enabling users to set the mistral conversation component api endpoint. This is useful for Azure configurability.

go test -v -tags=conftests -count=1 ./tests/conformance -run="TestConversationConformance/mistral"                            
=== RUN   TestConversationConformance
=== RUN   TestConversationConformance/mistral
=== RUN   TestConversationConformance/mistral/init
=== RUN   TestConversationConformance/mistral/converse
=== RUN   TestConversationConformance/mistral/converse/get_a_non-empty_response_without_errors
=== RUN   TestConversationConformance/mistral/converse/test_user_message_type
=== RUN   TestConversationConformance/mistral/converse/test_system_message_type
=== RUN   TestConversationConformance/mistral/converse/test_assistant_message_type
=== RUN   TestConversationConformance/mistral/converse/test_developer_message_type
=== RUN   TestConversationConformance/mistral/converse/test_tool_message_type_-_confirming_active_tool_calling_capability_(empty_tool_choice)
=== RUN   TestConversationConformance/mistral/converse/test_conversation_history_with_tool_calls
--- PASS: TestConversationConformance (34.71s)
    --- PASS: TestConversationConformance/mistral (34.71s)
        --- PASS: TestConversationConformance/mistral/init (0.00s)
        --- PASS: TestConversationConformance/mistral/converse (34.70s)
            --- PASS: TestConversationConformance/mistral/converse/get_a_non-empty_response_without_errors (0.66s)
            --- PASS: TestConversationConformance/mistral/converse/test_user_message_type (0.65s)
            --- PASS: TestConversationConformance/mistral/converse/test_system_message_type (0.51s)
            --- PASS: TestConversationConformance/mistral/converse/test_assistant_message_type (0.44s)
            --- PASS: TestConversationConformance/mistral/converse/test_developer_message_type (0.70s)
            --- PASS: TestConversationConformance/mistral/converse/test_tool_message_type_-_confirming_active_tool_calling_capability_(empty_tool_choice) (30.81s)
            --- PASS: TestConversationConformance/mistral/converse/test_conversation_history_with_tool_calls (0.93s)
PASS
ok      github.com/dapr/components-contrib/tests/conformance    35.809s

references for endpoint default
https://orkes.io/content/integrations/ai-llm/mistral#:~:text=Get%20the%20required%20credentials%20from,and%20enter%20the%20following%20parameters:

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #4056

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation
  • Created the dapr/docs PR:

Note: We expect contributors to open a corresponding documentation PR in the dapr/docs repository. As the implementer, you are the best person to document your work! Implementation PRs will not be merged until the documentation PR is opened and ready for review.

[cicoyle]

Can you open a docs PR for the metadata change here?

Also, could you add a small test to verify this?

I prefer ptrs for optional fields, but I do see all the other fields are also strings, so for consistency its fine, but in the future we should consider making the optional fields ptrs.