Refactor pkg/lmcli/provider

Moved `ChangeCompletionInterface` to `pkg/api`, moved individual
providers to `pkg/api/provider`

pkg/api/api.go

@@ -0,0 +1,35 @@
+package api
+
+import (
+	"context"
+
+	"git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
+)
+
+type ReplyCallback func(model.Message)
+
+type Chunk struct {
+	Content string
+}
+
+type ChatCompletionClient interface {
+	// CreateChatCompletion requests a response to the provided messages.
+	// Replies are appended to the given replies struct, and the
+	// complete user-facing response is returned as a string.
+	CreateChatCompletion(
+		ctx context.Context,
+		params model.RequestParameters,
+		messages []model.Message,
+		callback ReplyCallback,
+	) (string, error)
+
+	// Like CreateChageCompletion, except the response is streamed via
+	// the output channel as it's received.
+	CreateChatCompletionStream(
+		ctx context.Context,
+		params model.RequestParameters,
+		messages []model.Message,
+		callback ReplyCallback,
+		output chan<- Chunk,
+	) (string, error)
+}