adding config option for table and incremental materializaions

dbt/include/bigquery/macros/materializations/incremental.sql

@@ -86,6 +86,8 @@
 
   {{ run_hooks(pre_hooks) }}
 
+  {{ bigquery__run_script_headers(config.get('script_headers')) }}
+
   {% if partition_by.copy_partitions is true and strategy != 'insert_overwrite' %} {#-- We can't copy partitions with merge strategy --#}
         {% set wrong_strategy_msg -%}
         The 'copy_partitions' option requires the 'incremental_strategy' option to be set to 'insert_overwrite'.

dbt/include/bigquery/macros/materializations/table.sql

@@ -11,6 +11,8 @@
 
   {{ run_hooks(pre_hooks) }}
 
+  {{ bigquery__run_script_headers(config.get('script_headers')) }}
+
   {#
       We only need to drop this thing if it is not a table.
       If it _is_ already a table, then we can overwrite it without downtime

dbt/include/bigquery/macros/utils/run_script_headers.sql

@@ -0,0 +1,21 @@
+{% macro bigquery__run_script_headers(script_headers) %}
+    {%- if script_headers is not none -%}
+        {%- if script_headers is string -%}
+            {%- set script_headers = [script_headers] -%}
+        {%- endif -%}
+
+        {%- set formatted_script_headers = [] -%}
+
+        {%- for script_header in script_headers -%}
+            {%- set trimmed_script_header = script_header.strip() -%}
+            {%- if not trimmed_script_header.endswith(';') -%}
+                {%- set formatted_script_header = trimmed_script_header ~ ';' -%}
+            {%- else -%}
+                {%- set formatted_script_header = trimmed_script_header -%}
+            {%- endif -%}
+            {%- do formatted_script_headers.append(formatted_script_header) -%}
+        {%- endfor -%}
+
+        {{ formatted_script_headers | join('\n') }}
+    {%- endif -%}
+{%- endmacro -%}