feat: mpe_validations table and a note about the pgmloc var in hook scripts

docs/dcc-tables.md

@@ -212,7 +212,6 @@ The code is simply `%include`'d at the relevant point during backend execution.
 * Physical, ie the full path to a `.sas` program on the physical server directory
 * Logical, ie a Viya Job (SAS Drive), SAS 9 Stored Process (Metadata Folder) or SASJS Stored Program (SASjs Drive).
 
-
 If the entry ends in `".sas"` it is assumed to be a physical, filesystem file.  Otherwise, the source code is extracted from SAS Drive or Metadata.
 
 To illustrate:
@@ -220,5 +219,7 @@ To illustrate:
 * Physical filesystem (ends in .sas):  `/opt/sas/code/myprogram.sas`
 * Logical filesystem:  `/Shared Data/stored_processes/mydatavalidator`
 
+You can access the path to hook script at runtime (ie, in the HOOK script SAS code) using the `PGMLOC` macro variable.
+
 !!! warning
     Do not place your hook scripts inside the Data Controller (logical) application folder, as they may be inadvertently lost during a deployment (eg in the case of a backup-and-deploy-new-instance approach).

docs/tables/mpe_validations.md

@@ -0,0 +1,25 @@
+---
+layout: article
+title: MPE_VALIDATIONS
+description: The `MPE_VALIDATIONS` table enables a number of validations to be applied to the data at the point of entry - such as casing, min/max values, nullability, and the ability to generate dropdown values directly from source tables or dynamically from SAS programs.
+og_image: /img/mpe_validations.png
+---
+
+# MPE_VALIDATIONS
+
+The `MPE_VALIDATIONS` table enables a number of validations to be applied to the data at the point of entry - such as casing, min/max values, nullability, and the ability to generate dropdown values directly from source tables or dynamically from SAS programs.
+
+A detailed breakdown is available in the [validations](/dc-validations/) section.
+
+![validations](/img/mpe_validations.png)
+
+## Columns
+
+ - 🔑`TX_FROM num`: SCD2 open datetime
+ - `TX_TO num`: SCD2 close datetime
+ - 🔑 `BASE_LIB char(8)`: SAS Libref (8 chars)
+ - 🔑 `BASE_DS char(32)`: The library member name
+ - 🔑 `BASE_COL char(32)`: The column name
+ - 🔑 `RULE_TYPE char(32)`: The name of the rule to apply.
+ - `RULE_VALUE char(128)`: The value of the rule
+ - `RULE_ACTIVE num`: Set to 1 for an active rule.  Set to 0 to disable the rule.