[patch] Add captcha (PyCAPTCHA) support for new user registration

[roadrunner]

This is similar to #2707 in that it add a captcha to the registration page, but it uses ​PyCAPTCHA instead. Also, this patch is for trac 0.10 .

[roadrunner]

Patch to add captcha support to registration

[Rob van der Linde]

Thanks, this patch works a charm for trac 0.10

Might want to mention you need to add this to trac.ini

[account-manager] use_captcha = true

Other than that, great patch, simple and effective

[Steffen Hoffmann]

Replying to roadrunner:

This is similar to #2707 in that it add a captcha to the registration page, but it uses ​PyCAPTCHA instead. Also, this patch is for trac 0.10 .

Thanks for your contribution. I'll come back later and have a closer look, on how to do even a concurrent implementation together with the other captcha support.

[Steffen Hoffmann]

Replying to robvdl:

![...] Might want to mention you need to add this to trac.ini

Right, but to be more visible, do it with proper wiki formatting like so:

 [account-manager]
 use_captcha = true

[Steffen Hoffmann]

There is a SimpleCaptchaPlugin for captcha (Skimpy Gimpy) support as well. Cite from the SimpleCaptchaPlugin wiki page:

The plugin requires that AccountManagerPlugin has been patched to include an IRegistrationConfirmation extension point by the RegistrationConfirmationPatch.

[Steffen Hoffmann]

(In [11917]) AccountManagerPlugin: Add interface for configurable user registration procedure, refs #874, #2707, #2897, #4651, #5295, #7577, #8076.

The current user registration process lacks flexibility, as can be witnessed by the history of one of the oldest still pending tickets for this plugin: #874.

[Steffen Hoffmann]

(In [11923]) AccountManagerPlugin: Finish registration check rewrite, refs #874, #2707, #2897, #4651, #5295, #7577, #8076.

Now moving check execution into AccountManager, and _create_user() is gone, replaced by more clearly structured and modularized code.

Registration checking for requests from the admin panel is re-activated and minor improvements related to RegistrationError processing done too.

Note: The test, that detected admin requests to skip additional checking of existing permissions for each new username, has been done differently. In the future each check has to decide on its own, like this is done in the UsernamePermCheck now.