Merge #83: Refactor handle_environment_creation() using Steps Pattern

c8931b0 refactor: extract helper functions from handle_environment_creation (copilot-swe-agent[bot])
3e742ed Initial plan (copilot-swe-agent[bot])

Pull request description:

  The `handle_environment_creation()` function mixed configuration loading, command execution, and result display in a single 58-line function, violating SRP and making individual steps untestable.

  ## Changes

  **Main function refactored to orchestration-only (21 lines):**
  ```rust
  pub fn handle_environment_creation(
      env_file: &Path,
      working_dir: &Path,
  ) -> Result<(), CreateSubcommandError> {
      let mut ctx = CommandContext::new(working_dir.to_path_buf());

      // Step 1: Load configuration
      let config = load_configuration(ctx.output(), env_file)?;

      // Step 2: Execute command
      let environment = {
          let repository = ctx.repository().clone();
          let clock = ctx.clock().clone();
          execute_create_command(ctx.output(), config, repository, clock)?
      };

      // Step 3: Display results
      display_creation_results(ctx.output(), &environment);

      Ok(())
  }
  ```

  **Extracted three focused helper functions:**
  - `load_configuration()` - Config loading and validation
  - `execute_create_command()` - Command handler creation and execution
  - `display_creation_results()` - Success message formatting

  **Added unit tests for each helper function:**
  - 3 tests for configuration loading (valid config, missing file, invalid JSON)
  - 2 tests for command execution (success, duplicate environment)
  - 1 test for result display
  - All 5 existing integration tests remain unchanged and passing

  No behavioral changes. Each step is now independently testable while maintaining the same user-facing behavior.

  <!-- START COPILOT CODING AGENT SUFFIX -->

  <details>

  <summary>Original prompt</summary>

  >
  > ----
  >
  > *This section details on the original issue you should resolve*
  >
  > <issue_title>Refactor handle_environment_creation() Using Steps Pattern</issue_title>
  > <issue_description>**Parent Issue**: #63
  > **Type**: 🔨 Structural Improvement
  > **Impact**: 🟢🟢🟢 High
  > **Effort**: 🔵🔵🔵 High
  > **Priority**: P1
  > **Depends On**: #67 (Proposal 4)
  >
  > ## Problem
  >
  > The `handle_environment_creation()` function is 110+ lines and does too much:
  >
  > ```rust
  > fn handle_environment_creation(env_file: &Path, working_dir: &Path)
  >     -> Result<(), CreateSubcommandError>
  > {
  >     // 1. Create user output
  >     // 2. Load configuration
  >     // 3. Validate configuration
  >     // 4. Create repository
  >     // 5. Create clock
  >     // 6. Create command handler
  >     // 7. Execute command
  >     // 8. Display results
  >     // All in one function! 110+ lines
  > }
  > ```
  >
  > This violates SRP and makes the function hard to test and understand.
  >
  > ## Proposed Solution
  >
  > Break down into focused step functions:
  >
  > ```rust
  > pub fn handle_environment_creation(
  >     env_file: &Path,
  >     working_dir: &Path,
  > ) -> Result<(), CreateSubcommandError> {
  >     let mut output = output::create_default();
  >
  >     // Step 1: Load configuration
  >     let config = load_configuration(&mut output, env_file)?;
  >
  >     // Step 2: Create dependencies
  >     let context = CommandContext::new(working_dir.to_path_buf());
  >
  >     // Step 3: Execute command
  >     let environment = execute_create_command(&mut output, config, &context)?;
  >
  >     // Step 4: Display results
  >     display_creation_results(&mut output, &environment);
  >
  >     Ok(())
  > }
  >
  > fn load_configuration(output: &mut UserOutput, env_file: &Path)
  >     -> Result<EnvironmentCreationConfig, CreateSubcommandError>
  > {
  >     // Focused on configuration loading only
  > }
  >
  > fn execute_create_command(
  >     output: &mut UserOutput,
  >     config: EnvironmentCreationConfig,
  >     context: &CommandContext,
  > ) -> Result<Environment, CreateSubcommandError>
  > {
  >     // Focused on command execution only
  > }
  >
  > fn display_creation_results(output: &mut UserOutput, environment: &Environment) {
  >     // Focused on result display only
  > }
  > ```
  >
  > ## Benefits
  >
  > - ✅ Main function reduced from 110+ to ~25 lines
  > - ✅ Each step is self-contained and testable
  > - ✅ Clear orchestration flow
  > - ✅ Easier to modify individual steps
  > - ✅ Better error handling with clear error context
  >
  > ## Implementation Checklist
  >
  > - [ ] Create helper function `load_configuration()`
  > - [ ] Create helper function `execute_create_command()`
  > - [ ] Create helper function `display_creation_results()`
  > - [ ] Refactor main `handle_environment_creation()` to orchestrate steps
  > - [ ] Add comprehensive documentation to each function
  > - [ ] Write unit tests for each helper function
  > - [ ] Update integration tests to verify end-to-end behavior
  > - [ ] Verify all existing tests still pass
  > - [ ] Run linter and fix issues
  >
  > ## Acceptance Criteria
  >
  > - [ ] `handle_environment_creation()` is orchestration-only (~25 lines)
  > - [ ] Each step has its own focused function
  > - [ ] All steps have unit tests
  > - [ ] Integration tests verify end-to-end flow
  > - [ ] No behavioral changes from user perspective
  > - [ ] All tests pass: `cargo test create::subcommands::environment`
  > - [ ] Pre-commit checks pass: `./scripts/pre-commit.sh`
  > - [ ] Code follows project conventions
  >
  > ## Related Documentation
  >
  > - [Module Organization Guide](https://github.com/torrust/torrust-tracker-deployer/blob/main/docs/contributing/module-organization.md)
  > - [Refactor Plan](https://github.com/torrust/torrust-tracker-deployer/blob/main/docs/refactors/plans/presentation-commands-cleanup.md)</issue_description>
  >
  > ## Comments on the Issue (you are @copilot in this section)
  >
  > <comments>
  > </comments>
  >

  </details>

  - Fixes #69

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ACKs for top commit:
  josecelano:
    ACK c8931b0

Tree-SHA512: 7f46bfb7ee88e958ebd59a107ce0dd7abf12f337f4c16f0dfc929a463eabaa08c9c9e986deda35cdecc449feb25117759b0182a891fa38ac8aa5587b97a965f5

Author: josecelano