fix: pass external_id for credential process and IAM (#790)

Author: eoinsha

pkg/cfaws/assumer_aws_credential_process.go

@@ -76,6 +76,9 @@ func (cpa *CredentialProcessAssumer) AssumeTerminal(ctx context.Context, c *Prof
 				aro.TokenProvider = MfaTokenProvider
 			}
 			aro.Duration = configOpts.Duration
+			if c.AWSConfig.ExternalID != "" {
+				aro.ExternalID = &c.AWSConfig.ExternalID
+			}
 		})
 		return stsp.Retrieve(ctx)
 	}

pkg/cfaws/assumer_aws_iam.go

@@ -98,7 +98,9 @@ func (aia *AwsIamAssumer) AssumeTerminal(ctx context.Context, c *Profile, config
 				aro.TokenProvider = MfaTokenProvider
 			}
 			aro.Duration = configOpts.Duration
-
+			if c.AWSConfig.ExternalID != "" {
+				aro.ExternalID = &c.AWSConfig.ExternalID
+			}
 			/**If the mfa_serial is defined on the root profile, we need to set it in this config so that the aws SDK knows to prompt for MFA token:
 			*[profile base]
 			*region             = us-west-2