update links with main branch

- links now point to the `main` branch

Author: dfarrow0

docs/epidata_development.md

@@ -6,11 +6,11 @@ nav_order: 4
 # Epidata API Development Guide
 
 **Prerequisite:** this guide assumes that you have read the
-[frontend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/frontend_development.md).
+[frontend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/frontend_development.md).
 
 This guide describes how to write and test code for the Epidata API. For
 preliminary steps,
-[install docker and create a virtual network](https://github.com/cmu-delphi/operations/blob/master/docs/frontend_development.md#setup).
+[install docker and create a virtual network](https://github.com/cmu-delphi/operations/blob/main/docs/frontend_development.md#setup).
 
 After reading this guide, you may want to visit
 [the `fluview_meta` tutorial](new_endpoint_tutorial.md) for an example of how
@@ -28,7 +28,7 @@ You likely won't need to modify the `operations` repo, so cloning directly from
 `cmu-delphi` is usually sufficient. However, since you _are_ going to be
 modifying `delphi-epidata` sources, you'll first need to fork the repository
 and then clone your personal fork. For more details, see the Delphi-specific
-[discussion on forking and branching](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md#everyone).
+[discussion on forking and branching](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md#everyone).
 
 Here's an example of how to setup your local workspace. Note that you will need
 to use your own GitHub username where indicated.
@@ -124,9 +124,9 @@ docker run --rm -p 127.0.0.1:10080:80 \
 Unit tests are self-contained, and do not depend on external services like
 databases or web servers. You can run unit tests at any time according to the
 instructions in the
-[backend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md).
+[backend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md).
 
-First, [build the `delphi_python` image](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md#creating-an-image).
+First, [build the `delphi_python` image](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md#creating-an-image).
 Your test sources will live in, and be executed from within, this image.
 
 Then run the tests in a container based on that image:
@@ -242,7 +242,7 @@ point for additional tests. For example, see the tests for the
 
 To run the existing tests and any new tests that you write, you must
 follow the
-[backend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md)
+[backend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md)
 _within the same workspace_, so that the `delphi_python` image is created with
 any changes you have made (e.g. adding new integration tests). That image will
 contain the test driver and the source code of your integration tests. Then,
@@ -259,7 +259,7 @@ More concretely, you can run Epidata API integration tests like this:
   above.
 
 3. Build the `delphi_python` image per the
-  [backend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md#creating-an-image).
+  [backend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md#creating-an-image).
   Your test sources will live in, and be executed from within, this image.
 
 4. Run integration tests in a container based on the `delphi_python` image:
@@ -297,7 +297,7 @@ This allows your code changes to be reflected immediately, without needing to
 rebuild containers.
 
 There are some drawbacks however, as discussed in the
-[Epicast development guide](https://github.com/cmu-delphi/www-epicast/blob/master/docs/epicast_development.md#develop).
+[Epicast development guide](https://github.com/cmu-delphi/www-epicast/blob/main/docs/epicast_development.md#develop).
 For example:
 
 - Code running in the container is able to read (and possibly also write) your local filesystem.

docs/new_endpoint_tutorial.md

@@ -21,7 +21,7 @@ In this tutorial we'll create a brand new endpoint for the Epidata API:
 # setup
 
 Follow
-[the backend guide](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md)
+[the backend guide](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md)
 and [the epidata guide](epidata_development.md) to install Docker and get your
 workspace ready for development. Before continuing, your workspace should look
 something like the following:
@@ -174,7 +174,7 @@ Now that we've changed several files, we need to make sure that the changes
 work as intended _before_ submitting code for review or committing code to the
 repository. Given that the code spans multiple components and languages, this
 needs to be an integration test. See more about integration testing in Delphi's
-[frontend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/frontend_development.md#integration).
+[frontend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/frontend_development.md#integration).
 
 Create an integration test for the new endpoint by creating a new file
 `integrations/server/test_fluview_meta.py`. There's a good amount of
@@ -245,7 +245,7 @@ the following row in the appropriate place (i.e. next to the row for
 Finally, we just need to run all new and existing tests. It is recommended to
 start with the unit tests because they are faster to build, run, and either
 succeed or fail. Follow the
-[backend development guide](https://github.com/cmu-delphi/operations/blob/master/docs/backend_development.md#running-a-container).
+[backend development guide](https://github.com/cmu-delphi/operations/blob/main/docs/backend_development.md#running-a-container).
 In summary:
 
 ```bash