Sending email to 20 contacts registers 20 activity records in sender's activity log

This issue will be continued on 2.2, with adding new columns to civicrm_activity_assignment and civicrm_activity_target, where assignee and target specific emails will be stored. Below is the diff for schema changes, and remarks from Piotr on specific ideas on storing email messages.

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Modified: trunk/xml/schema/Activity/ActivityAssignment.xml
===================================================================
— trunk/xml/schema/Activity/ActivityAssignment.xml 2008-07-15 13:36:41 UTC (rev 15816)
+++ trunk/xml/schema/Activity/ActivityAssignment.xml 2008-07-15 14:24:54 UTC (rev 15817)
@@ -86,6 +86,24 @@
<onDelete>CASCADE</onDelete>
</foreignKey>

+ <field>
+ <name>subject</name>
+ <type>varchar</type>
+ <length>255</length>
+ <comment>The subject/purpose/short description of the activity, used if specific to Assignee.</comment>
+ <import>true</import>
+ <add>2.1</add>
+ </field>
+
+ <field>
+ <name>details</name>
+ <title>Details</title>
+ <import>true</import>
+ <type>text</type>
+ <comment>Details about the activity (agenda, notes, etc), used if specific to Assignee.</comment>
+ <add>2.1</add>
+ </field>
+
<index>
<name>UI_activity_assignee_contact_id</name>
<fieldName>assignee_contact_id</fieldName>

Modified: trunk/xml/schema/Activity/ActivityTarget.xml
===================================================================
— trunk/xml/schema/Activity/ActivityTarget.xml 2008-07-15 13:36:41 UTC (rev 15816)
+++ trunk/xml/schema/Activity/ActivityTarget.xml 2008-07-15 14:24:54 UTC (rev 15817)
@@ -50,6 +50,24 @@
<onDelete>CASCADE</onDelete>
</foreignKey>

+ <field>
+ <name>subject</name>
+ <type>varchar</type>
+ <length>255</length>
+ <comment>The subject/purpose/short description of the activity, used if specific to Target.</comment>
+ <import>true</import>
+ <add>2.1</add>
+ </field>
+
+ <field>
+ <name>details</name>
+ <title>Details</title>
+ <import>true</import>
+ <type>text</type>
+ <comment>Details about the activity (agenda, notes, etc), used if specific to Target.</comment>
+ <add>2.1</add>
+ </field>
+
<index>
<name>UI_activity_target_contact_id</name>
<fieldName>target_contact_id</fieldName>

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In case of 'email activities', the 'details' field should host
both text and HTML versions together; would it make sense to define it
to simply host the encoded body of the email?

The other solution is to have these two parts hosted there 'unprocessed
for email', separated by ^A for example; this is easier to display and
store. The first solution is harder to display, but more 'true' - if we
keep them 'processed', we know how stuff got encoded, lines wrapped,
etc.

===

We need to investigate possibility to register only single activity record in sender's activity list. Currently, activities become less useful because of clutter caused by many positions in the list.

Disable delete activity if activity type = email.