docs(server): add server readme with initial coding guidelines (#2720)

server/README.md

@@ -0,0 +1,27 @@
+# Server architecture and coding guidelines
+
+## Basic code organization rules
+
+### 1. Resources
+
+- `resource_name` must be singular. **snake_case** for filenames, **CamelCaseUpperFirst** for struct names.
+- Resource package names must be in **singular**.
+- Resource files must be named `{resource_name}_entities.go` and  `{resource_name}_repository.go`
+  > This format makes it easy to fuzzy search files
+- `{resource_name}_entities.go` must contain only one "main" entity and zero or more sub-entities (i.e. [demoresource](https://github.com/kubeshop/tracetest/blob/main/server/config/demoresource/demo_resource.go))
+- Resource packages can have one or  more "main" entities, each living on its own file. For example, the `transactions` package could have `transaction_entities.go` and `transaction_runs_entities.go`
+- Resource packages can have "subpackages". All the same rules apply. The package must **NOT** be prefixed with the parent package (i.e. `test/trigger` is good, `test/testtrigger` is bad), with the exception of generic names (i.e. `test/util` should be `test/testutil`)
+
+Example tests resource package:
+
+```
+test/
+	trigger/
+		trigger_entities.go	
+		http_entities.go
+
+	test_repository.go
+	test_entities.go
+	test_run_repository.go
+	test_run_entities.go
+```

wiki/README.md

@@ -3,4 +3,5 @@
 
 ## Architecture 
 
-1. [Resource Manager](../server/resourcemanager/README.md)
+1. [General guidelines](../server/README.md)
+2. [Resource Manager](../server/resourcemanager/README.md)