Live terminal output (#5396)

* Add /logs/raw and /logs/subscribe for getting logs on frontend
Hijacks stderr/stdout to send all output data to the client on flush

* Use existing send sync method

* Fix get_logs should return string

* Fix bug

* pass no server

* fix tests

* Fix output flush on linux

api_server/services/terminal_service.py

@@ -0,0 +1,47 @@
+from app.logger import on_flush
+import os
+
+
+class TerminalService:
+    def __init__(self, server):
+        self.server = server
+        self.cols = None
+        self.rows = None
+        self.subscriptions = set()
+        on_flush(self.send_messages)
+
+    def update_size(self):
+        sz = os.get_terminal_size()
+        changed = False
+        if sz.columns != self.cols:
+            self.cols = sz.columns
+            changed = True 
+
+        if sz.lines != self.rows:
+            self.rows = sz.lines
+            changed = True
+
+        if changed:
+            return {"cols": self.cols, "rows": self.rows}
+
+        return None
+
+    def subscribe(self, client_id):
+        self.subscriptions.add(client_id)
+
+    def unsubscribe(self, client_id):
+        self.subscriptions.discard(client_id)
+
+    def send_messages(self, entries):
+        if not len(entries) or not len(self.subscriptions):
+            return
+        
+        new_size = self.update_size()
+        
+        for client_id in self.subscriptions.copy(): # prevent: Set changed size during iteration
+            if client_id not in self.server.sockets:
+                # Automatically unsub if the socket has disconnected
+                self.unsubscribe(client_id)
+                continue
+
+            self.server.send_sync("logs", {"entries": entries, "size": new_size}, client_id)