Document tag_bindings definition as map(string) (#2777)

adrs/20241029-versioning.md

@@ -1,6 +1,6 @@
 # Versioning Scheme Tied to FAST Releases
 
-**authors:** [Ludo](https://github.com/ludoo),  [Julio](https://github.com/jccb), [Simone](https://github.com/sruffilli) \
+**authors:** [Ludo](https://github.com/ludoo),  [Julio](https://github.com/juliocc), [Simone](https://github.com/sruffilli) \
 **date:** Oct 29, 2024
 **last update**: Oct 30, 2024
 

adrs/20241219-tag-bindings.md

@@ -0,0 +1,35 @@
+# Using `map(string)` for `tag_bindings` variables
+
+**authors:** [Julio](https://github.com/juliocc)
+**date:** Dec 19, 2024
+
+## Status
+
+Accepted and implemented.
+
+## Context
+
+We need to define a variable to manage tag bindings in our Terraform modules. This variable will be used across various modules and within the FAST framework to attach tags to resources via the `google_tags_tag_binding` resource.  This variable needs to support both statically defined tags and tags that are dynamically generated during the apply phase of Terraform.
+
+## Decision:
+
+We will use the `map(string)` type for the `tag_bindings` variable across all modules where it's needed. 
+
+## Consequences
+
+Minimal. This is already an established practice across the repository.
+
+Note that the keys of the map are ignored by our code and only used to bypass Terraform limitations with dynamic values in a `for_each` argument.  See [Using Expressions in for_each](https://developer.hashicorp.com/terraform/language/meta-arguments/for_each#using-expressions-in-for_each) in Terraform's documentation for more details.
+
+## Reasoning
+
+The primary reason for choosing `map(string)` is to enable the use of dynamic tags without encountering Terraform errors related to dynamic values.  By using a map, we avoid the limitations imposed by lists or sets and ensure that our modules and FAST can handle both static and dynamic tag values.
+
+## Alternatives Considered:
+
+- `list(string)`: Lists would enforce a fixed number of tags defined at plan time, limiting flexibility and hindering the management of dynamic tags.
+- `set(string)`: Similar to lists, sets would require all tag values to be known at plan time, which is not suitable for scenarios with dynamic tag generation.
+
+## Implementation:
+
+At the time of writing this ADR, all modules and FAST stages already use `map(string)`. The purpose of this ADR is to document an existing practice.

adrs/fast/1-network-ranges.md

@@ -1,6 +1,6 @@
 # IP ranges for network stages
 
-**authors:** [Ludo](https://github.com/ludoo), [Roberto](https://github.com/drebes), [Julio](https://github.com/jccb) \
+**authors:** [Ludo](https://github.com/ludoo), [Roberto](https://github.com/drebes), [Julio](https://github.com/juliocc) \
 **date:** Sept 20, 2023
 
 ## Status

adrs/modules/20231106-factories.md

@@ -5,7 +5,7 @@
 
 ## Status
 
-Under discussion.
+Accepted and implemented.
 
 ## Context