Stop trimming trailing slashes from MCP server URLs on save. Some MCP
servers (e.g. Bitrix24) require a trailing slash; removing it triggers a
301 redirect that drops Authorization headers, resulting in 400 errors.
The trailing-slash trim is now skipped when the connection type is 'mcp',
while OpenAPI connections continue to have it stripped as before.
Fixes open-webui#21179
Varun Chawla
24179cde2f