clarification about hivemq ca file

Author: sgbaird

docs/courses/hello-world/1.1-running-the-demo.ipynb

@@ -18,6 +18,10 @@
     "```{include} ./hardware-note.md\n",
     "```\n",
     "\n",
+    "```{warning}\n",
+    "Recently, HiveMQ Cloud changed such that `hivemq-com-chain.der` (a Certificate Authority (CA) file) is not transferrable across different broker instances. The [latest `hivemq-com-chain.der` file](https://raw.githubusercontent.com/sparks-baird/self-driving-lab-demo/main/src/public_mqtt_sdl_demo/hivemq-com-chain.der) from [`self-driving-lab-demo`](https://github.com/sparks-baird/self-driving-lab-demo) will be hard-coded to the `self-driving-lab-demo` public test credentials (i.e., what is used in Module 1 - Running the Demo), so the *tutorials* should run without issue as long as you are using that file. However, the *assignment* requires you to have your own HiveMQ Cloud broker instance, so you will need to [generate a `hivemq-com-chain.der` file specific to your instance](https://colab.research.google.com/github/sparks-baird/self-driving-lab-demo/blob/main/notebooks/7.2.1-hivemq-openssl-certificate.ipynb) and upload it to your microcontroller in place of the default one.\n",
+    "```\n",
+    "\n",
     "Learn how to build a Closed-loop Spectroscopy Lab: Light-mixing Demo (CLSLab:Light) to\n",
     "perform color matching via RGB LEDs and a light sensor for under 100 USD and less than an hour\n",
     "of setup. The tutorial covers ordering parts, verifying prerequisites, software setup, sensor\n",

docs/courses/hello-world/1.4-hardware-software-communication.ipynb

@@ -16,7 +16,7 @@
                 "## 🔰 Tutorial\n",
                 "\n",
                 "```{warning}\n",
-                "Recently, HiveMQ Cloud changed such that the Certificate Authority (CA) file, `hivemq-com-chain.der`, is not transferrable across different broker instances. The [latest `hivemq-com-chain.der` file](https://raw.githubusercontent.com/sparks-baird/self-driving-lab-demo/main/src/public_mqtt_sdl_demo/hivemq-com-chain.der) from [`self-driving-lab-demo`](https://github.com/sparks-baird/self-driving-lab-demo) will be hard-coded to the `self-driving-lab-demo` public test credentials (i.e., what is used in Module 1 - Running the Demo), so the tutorials should run without issue as long as you are using that file. However, the assignment requires you to create your own HiveMQ Cloud broker instance, so you will need to follow the assignment README instructions there to generate your a `hivemq-com-chain.der` file specific to your instance.\n",
+                "Recently, HiveMQ Cloud changed such that `hivemq-com-chain.der` (a Certificate Authority (CA) file) is not transferrable across different broker instances. The [latest `hivemq-com-chain.der` file](https://raw.githubusercontent.com/sparks-baird/self-driving-lab-demo/main/src/public_mqtt_sdl_demo/hivemq-com-chain.der) from [`self-driving-lab-demo`](https://github.com/sparks-baird/self-driving-lab-demo) will be hard-coded to the `self-driving-lab-demo` public test credentials (i.e., what is used in Module 1 - Running the Demo), so the *tutorials* should run without issue as long as you are using that file. However, the *assignment* requires you to have your own HiveMQ Cloud broker instance, so you will need to [generate a `hivemq-com-chain.der` file specific to your instance](https://colab.research.google.com/github/sparks-baird/self-driving-lab-demo/blob/main/notebooks/7.2.1-hivemq-openssl-certificate.ipynb) and upload it to your microcontroller in place of the default one.\n",
                 "```\n",
                 "\n",
                 "In this tutorial, you will learn how to send commands to and receive sensor data from a microcontroller using the MQTT protocol.\n",

docs/courses/hello-world/1.6-connecting-the-pieces.ipynb

@@ -19,6 +19,10 @@
     "As a temporary workaround to the issue described in https://github.com/orgs/micropython/discussions/15112, add [`urequests_2.py`](https://github.com/AccelerationConsortium/ac-microcourses/blob/main/docs/courses/hello-world/urequests_2.py) [[permalink](https://github.com/AccelerationConsortium/ac-microcourses/blob/e5541ce3ec307a8e5e0f2b20f000c03f040e1f56/docs/courses/hello-world/urequests_2.py)] to your microcontroller, and change `import urequests` to `import urequests_2 as urequests` in the code below. See https://github.com/orgs/micropython/discussions/15112 and https://github.com/micropython/micropython-lib/pull/861 for ongoing updates. The corresponding assignment will also be affected, but this can be addressed using the same workaround.\n",
     "```\n",
     "\n",
+    "```{warning}\n",
+    "Recently, HiveMQ Cloud changed such that `hivemq-com-chain.der` (a Certificate Authority (CA) file) is not transferrable across different broker instances. The [latest `hivemq-com-chain.der` file](https://raw.githubusercontent.com/sparks-baird/self-driving-lab-demo/main/src/public_mqtt_sdl_demo/hivemq-com-chain.der) from [`self-driving-lab-demo`](https://github.com/sparks-baird/self-driving-lab-demo) will be hard-coded to the `self-driving-lab-demo` public test credentials (i.e., what is used in Module 1 - Running the Demo), so the *tutorials* should run without issue as long as you are using that file. However, the *assignment* requires you to have your own HiveMQ Cloud broker instance, so you will need to [generate a `hivemq-com-chain.der` file specific to your instance](https://colab.research.google.com/github/sparks-baird/self-driving-lab-demo/blob/main/notebooks/7.2.1-hivemq-openssl-certificate.ipynb) and upload it to your microcontroller in place of the default one.\n",
+    "```\n",
+    "\n",
     "You've made it to the final module of this microcourse! Well done 🥳. In this module, you will connect the pieces from previous modules into the \"Hello World\" of self-driving labs, from microcontroller programming and Bayesian optimization to hardware-software communication and data logging.\n",
     "\n",
     "<img src=\"../../_static/connecting-pieces.png\" width=80%>\n",