/auto (#16696)

Add `/auto` behind a feature flag that's disabled for now, even for
staff.

We've decided on a different design for context inference, but there are
parts of /auto that will be useful for that, so we want them in the code
base even if they're unused for now.

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/semantic_index/src/embedding.rs

@@ -12,6 +12,12 @@ use futures::{future::BoxFuture, FutureExt};
 use serde::{Deserialize, Serialize};
 use std::{fmt, future};
 
+/// Trait for embedding providers. Texts in, vectors out.
+pub trait EmbeddingProvider: Sync + Send {
+    fn embed<'a>(&'a self, texts: &'a [TextToEmbed<'a>]) -> BoxFuture<'a, Result<Vec<Embedding>>>;
+    fn batch_size(&self) -> usize;
+}
+
 #[derive(Debug, Default, Clone, PartialEq, Serialize, Deserialize)]
 pub struct Embedding(Vec<f32>);
 
@@ -68,12 +74,6 @@ impl fmt::Display for Embedding {
     }
 }
 
-/// Trait for embedding providers. Texts in, vectors out.
-pub trait EmbeddingProvider: Sync + Send {
-    fn embed<'a>(&'a self, texts: &'a [TextToEmbed<'a>]) -> BoxFuture<'a, Result<Vec<Embedding>>>;
-    fn batch_size(&self) -> usize;
-}
-
 #[derive(Debug)]
 pub struct TextToEmbed<'a> {
     pub text: &'a str,