Update config/constants.php with defined() checks
Allows for easier override with an environment-based configs.
Close #4045
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 4988157..971a234 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -7,6 +7,10 @@
Release Date: Not Released
+- General Changes
+
+ - Updated the *application/config/constants.php* file to check if constants aren't already defined before doing that.
+
Bug fixes for 3.0.2
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